Quantum Chemistry

The biochemistry of geotropism in plants and gravisensing in e.g. cyanobacteria or paramacia is still not well understood today [1]. Perhaps there are more ways than one for organisms to sense gravity. The two best known relatively old explanations for gravity sensing are sensing through the redistribution of cellular starch statoliths and sensing through redistribution of auxin. The starch containing statoliths in a gravity field produce pressure on the endoplasmic reticulum of the cell. This enables the cell to sense direction. (...) Alternatively, there is the redistribution of auxin under the action of gravity. This is known as the Cholodny-Went hypothesis [2], [3]. The latter redistribution coincides with a redistribution of electrical charge in the cell. With the present study the aim is to add a mathematical unified field explanation to gravisensing. (shrink)

Science frequently gives us multiple, compatible ways of solving the same problem or formulating the same theory. These compatible formulations change our understanding of the world, despite providing the same explanations. According to what I call "conceptualism," reformulations change our understanding by clarifying the epistemic structure of theories. I illustrate conceptualism by analyzing a typical example of symmetry-based reformulation in chemical physics. This case study poses a problem for "explanationism," the rival thesis that differences in understanding require ontic explanatory differences. (...) To defend conceptualism, I consider how prominent accounts of explanation might accommodate this case study. I argue that either they do not succeed, or they generate a skeptical challenge. (shrink)

The article summarizes the software tool on astrophysical analysis with multi-wavelength space telescope data. It recaps the evidence analysis conducted on the Kerr-Newman black hole (KNBH). It was written prior to the article Research on the Kerr-Newman Black Hole in M82 Confirms Black Hole and White Hole Juxtapose not soon after the experiment. The conducted analysis suggested Hawking radiation is caused by the movement of ergosurfaces of the BH and serves as the primal evidence for black hole and white hole (...) juxtapose. A later data exploration was conducted with the radiation trails in the multi-wavelength data. The evidences produced corroborates with Yale professor Priyamvada Natarajan's black hole seeds theory. It implies that the electromagnetic dynamic of fusion and fission temperature determines the pressure of surface tension on the macro particles, and the mass density of the BH is determined by the electromagnetic tension between the outer ergosurface and inner ergosurface. The ring singularity of the BH and the Penrose-Hawking singularity of the BH determine the spin and gravitational singularity of the BH. Inside the ergosurfaces, the BH singularities' backward inflow causes the vicinity's rate on feeding the BH. It makes the active galactic nuclei (AGN) a semi-closed system. The density pressure is released on threshold. During the mass exchange observed by energy momentum upon the AGN's open, the macroparticle composition of the BH changes with the galactic event. This causes the expansion rate of the galaxy and contraction rate of the BH. AGN types and their relative motions determine the expansion rate of the cosmic universe in a generalized quantitative thinking. The article concludes that BH spin is caused by the asymmetric motions of AGN in the BH system. A set of the nuclear resonance caused by BH and white hole (WH) oscillation is processed with the same set of data. (shrink)

The ideas of quantum simulation and advances in quantum algorithms to solve quantum chemistry problems have been discussed. Theoretical proposals and experimental investigations both have been studied to gauge the extent to which quantum computation has been applied to solve quantum chemical problems till date. The distinctive features and limitations of the application of quantum simulation on chemical systems and current approaches to define and improve upon standard quantum algorithms have been studied in detail. The possibility and consequences of designing (...) an efficient quantum computer that can address chemical problems have been assessed. The experimental realization of quantum supremacy defies the conventional belief of chemists, that millions of qubits would be required to solve fundamental chemistry problems. It is predicted that quantum simulation of quantum chemistry problems will radically revolutionize this field. (shrink)

Computational reproducibility possesses its own dynamics and narratives of crisis. Alongside the difficulties of computing as an ubiquitous yet complex scientific activity, computational reproducibility suffers from a naive expectancy of total reproducibility and a moral imperative to embrace the principles of free software as a non-negotiable epistemic virtue. We argue that the epistemic issues at stake in actual practices of computational reproducibility are best unveiled by focusing on software as a pivotal concept, one that is surprisingly often overlooked in accounts (...) of reproducibility issues. Software is not only about designing and coding but also about maintaining, supporting, distributing, licensing, and governance; it is not only about developers but also about users. We focus on openness debates among computational chemists involved in molecular modeling software packages as empirical grounding for our argument. We then identify and analyse four epistemic characteristics as key to the role of software in computational reproducibility. (shrink)

The thesis is: the “periodic table” of “dark matter” is equivalent to the standard periodic table of the visible matter being entangled. Thus, it is to consist of all possible entangled states of the atoms of chemical elements as quantum systems. In other words, an atom of any chemical element and as a quantum system, i.e. as a wave function, should be represented as a non-orthogonal in general (i.e. entangled) subspace of the separable complex Hilbert space relevant to the system (...) to which the atom at issue is related as a true part of it. The paper follows previous publications of mine stating that “dark matter” and “dark energy” are projections of arbitrarily entangled states on the cognitive “screen” of Einstein’s “Mach’s principle” in general relativity postulating that gravitational field can be generated only by mass or energy. (shrink)

Within quantum chemistry, the electron clouds that surround nuclei in atoms and molecules are sometimes treated as clouds of probability and sometimes as clouds of charge. These two roles, tracing back to Schrödinger and Born, are in tension with one another but are not incompatible. Schrödinger’s idea that the nucleus of an atom is surrounded by a spread-out electron charge density is supported by a variety of evidence from quantum chemistry, including two methods that are used to determine atomic and (...) molecular structure: the Hartree-Fock method and density functional theory. Taking this evidence as a clue to the foundations of quantum physics, Schrödinger’s electron charge density can be incorporated into many different interpretations of quantum mechanics. (shrink)

Arthur Clark and Michael Kube–McDowell (“The Triger”, 2000) suggested the sci-fi idea about the direct transformation from a chemical substance to another by the action of a newly physical, “Trigger” field. Karl Brohier, a Nobel Prize winner, who is a dramatic persona in the novel, elaborates a new theory, re-reading and re-writing Pauling’s “The Nature of the Chemical Bond”; according to Brohier: “Information organizes and differentiates energy. It regularizes and stabilizes matter. Information propagates through matter-energy and mediates the interactions of (...) matter-energy.” Dr Horton, his collaborator in the novel replies: “If the universe consists of energy and information, then the Trigger somehow alters the information envelope of certain substances –“. “Alters it, scrambles it, overwhelms it, destabilizes it” Brohier adds. There is a scientific debate whether or how far chemistry is fundamentally reducible to quantum mechanics. Nevertheless, the fact that many essential chemical properties and reactions are at least partly representable in terms of quantum mechanics is doubtless. For the quantum mechanics itself has been reformulated as a theory of a special kind of information, quantum information, chemistry might be in turn interpreted in the same terms. Wave function, the fundamental concept of quantum mechanics, can be equivalently defined as a series of qubits, eventually infinite. A qubit, being defined as the normed superposition of the two orthogonal subspaces of the complex Hilbert space, can be interpreted as a generalization of the standard bit of information as to infinite sets or series. All “forces” in the Standard model, which are furthermore essential for chemical transformations, are groups [U(1),SU(2),SU(3)] of the transformations of the complex Hilbert space and thus, of series of qubits. One can suggest that any chemical substances and changes are fundamentally representable as quantum information and its transformations. If entanglement is interpreted as a physical field, though any group above seems to be unattachable to it, it might be identified as the “Triger field”. It might cause a direct transformation of any chemical substance by from a remote distance. Is this possible in principle? (shrink)

To this day, a hundred and fifty years after Mendeleev's discovery, the overal structure of the periodic system remains unaccounted for in quantum-mechanical terms. Given this dire situation, a handful of scientists in the 1970s embarked on a quest for the symmetries that lie hidden in the periodic table. Their goal was to explain the table's structure in group-theoretical terms. We argue that this symmetry program required an important paradigm shift in the understanding of the nature of chemical elements. The (...) idea, in essence, consisted of treating the chemical elements, not as particles, but as states of a superparticle. We show that the inspiration for this came from elementary particle physics, and in particular from Heisenberg's suggestion to treat the proton and neutron as different states of the nucleon. We provide a careful study of Heisenberg's last paper on the nature of elementary particles, and explain why the Democritean picture of matter no longer applied in modern physics and a Platonic symmetry-based picture was called for instead. We show how Heisenberg's Platonic philosophy came to dominate the field of elementary particle physics, and how it found its culmination point in Gell-Mann's classification of the hadrons in the eightfold way. We argue that it was the success of Heisenberg's approach in elementary particle physics that sparked the group-theoretical approach to the periodic table. We explain how it was applied to the set of chemical elements via a critical examination of the work of the Russian mathematician Abram Ilyich Fet the Turkish-American physicist Asim Orhan Barut, before giving some final reflections. (shrink)

. Computational chemistry grew in a new era of “desktop modeling,” which coincided with a growing demand for modeling software, especially from the pharmaceutical industry. Parameterization of models in computational chemistry is an arduous enterprise, and we argue that this activity leads, in this specific context, to tensions among scientists regarding the epistemic opacity transparency of parameterized methods and the software implementing them. We relate one flame war from the Computational Chemistry mailing List in order to assess in detail the (...) relationships between modeling methods, parameterization, software and the various forms of their enclosure or disclosure. Our claim is that parameterization issues are an important and often neglected source of epistemic opacity and that this opacity is entangled in methods and software alike. Models and software must be addressed together to understand the epistemological tensions at stake. (shrink)

The aim of this article is to present a different perspective through which to examine reduction and emergence; namely, the perspective of chemistry’s relation to physics.

This monograph deals with the interrelationship between chemistry and physics, and especially the role played by quantum chemistry as a theory in between these two disciplines. The author uses structuralist approach to explore the overlap between the two sciences, looking at their theoretical and ontological borrowings as well as their continuity. -/- The starting point of this book is that there is at least a form of unity between chemistry and physics, where the reduction relation is conceived as a special (...) case of this unity. However, matters are never concluded so simply within philosophy of chemistry, as significant problems exist around a number of core chemical ideas. Specifically, one cannot take the obvious success of quantum theories as outright support for a reductive relationship. Instead, in the context of a suitably adapted Nagelian framework for reduction, modern chemistry's relationship to physics is constitutive. The results provided by quantum chemistry, in particular, have significant consequences for chemical ontology. This book is ideal for students, scholars and academics from the field of Philosophy of Science, and particularly for those with an interest in Philosophy of Chemistry and Physics. (shrink)

Book Review of E. Thomas Strom & Angela K. Wilson : Pioneers of Quantum Chemistry, Washington/DC 2013.

This paper discusses how computational modeling combines the autonomy of models with the automation of computational procedures. In particular, the case of ab-initio methods in quantum chemistry will be investigated to draw two lessons from the analysis of computational modeling. The first belongs to general philosophy of science: Computational modeling faces a trade-off and enlarges predictive force at the cost of explanatory force. The other lesson is about the philosophy of chemistry: The methodology of computational modeling puts into doubt claims (...) about the reduction of chemistry to physics. (shrink)

Philosophers mainly refer to quantum chemistry in order to address questions about the reducibility or autonomy of chemistry relative to quantum physics, and to argue for or against ontological emergence. To make their point, they scrutinize quantum approximations and formalisms as if they were independent of the questions at stake. This paper proposes a return to history and to the laboratory so as to emphasize how quantum chemists never cease to negotiate the relationships between a molecule, its parts, and its (...) environment. This investigation will enable us to draw methodological conclusions about the role of history within philosophical studies, and to examine how quantum chemistry can clarify important philosophical and mereological issues related to the emergence/reduction debate, or to the way instruments and contexts are involved in the material making and the formal description of wholes and parts. (shrink)

In line with their previous studies dedicated to quantum chemistry (Gavroglu and Simões 1994, 2000; Simões and Gavroglu 1997, 2001), the last joint publication by Kostas Gavroglu and Ana Simões provides the readers not only with a fine-grained, rigorous, and highly valuable book on the history of science but also with stimulating epistemological insights about the way ‘in-between’ disciplines, to use the authors’ turn of phrase, emerge from the convergence of diverging ‘styles’ of research and heterogeneous practices. To make their (...) point, the authors divide their work into four main chapters before drawing epistemological and historiographical conclusions in the fifth and last part of their work. The first chapter entitled ‘Quantum Chemistry qua Physics: The Promises and Deadlocks of Using First Principles’ focuses mainly on German researchers’ contributions in the development of quantum chemistry. In this respect, it highlights four pioneering moments: (1) Walter Heitler and Fritz Lo. (shrink)

Contribution to a symposium on Kostas Gavroglu and Ana Simões, Neither Physics nor Chemistry, The MIT Press, Cambridge, Massachusetts.

This paper widens the scope of our previous paper (Harré and Llored in Found Chem 13:63–76, 2011) by scrutinizing how whole/parts relations are involved in the study of molecules. In doing so, we point out two mereological fallacies which endanger both philosophical and chemical inferences. We also further explore how the concept of affordance is related to our mereological investigation. We then refer to quantum chemistry in order to pave the way for a new mereological approach for chemistry.

In this paper I briefly reply to Shant Shahbazian’s comments on my paper “Austere quantum mechanics as a reductive basis for chemistry” and argue that quantum theory of atoms in molecules can be characterised as a research programme in the theories of chemistry. I also explore the areas in which Shahbazian and me agree and disagree.

The many-faced relationship between chemistry and physics is one of the most discussed topics in the philosophy of chemistry. In his recent book Reducing Chemistry to Physics. Limits, Models, Consequences, Hinne Hettema conceives this relationship as a reduction link, and devotes his work to defend this position on the basis of a “naturalized” concept of reduction. In the present paper I critically review three kinds of issues stemming from Hettema’s argumentation: philosophical, scientific and methodological.

At the heart of chemistry lies the periodic system of chemical elements. Despite being the cornerstone of modern chemistry, the overall structure of the periodic system has never been fully understood from an atomic physics point of view. Group-theoretical models have been proposed instead, but they suffer from several limitations. Among others, the identification of the correct symmetry group and its decomposition into subgroups has remained a problem to this day. In an effort to deepen our limited understanding of the (...) periodic law, we have extended the traditional Lie algebraic framework to account for the peculiar degeneracy structure of the periodic system. Starting from the four-dimensional hidden symmetry and accidental degeneracy of the hydrogen atom, as first revealed by Fock in 1935, our research has mainly focussed on the way this SO(4) symmetry of the Coulomb potential gets broken in the periodic system as a consequence of the transformation of the hydrogenic (n, l) filling order to the Madelung (n+l, n) order due to electronic repulsions, relativistic effects and spin-orbit couplings. In this PhD dissertation, a new left-step format of the periodic table is first proposed on the basis of the Madelung rule. Following the particle physics tradition, the chemical elements are then considered as various states of some 'atomic matter', which is described by a non-compact spectrum-generating dynamical Lie group. The chemical elements are shown to form a basis for a single infinite-dimensional degeneracy space of the SO(4,2) ⊗ SU(2) group. An explanation for the period doubling is then proposed in terms of a particular symmetry breaking of the SO(4,2) group to the anti de Sitter SO(3,2) group. The Madelung rule is rationalised on the basis of nonlinear Lie algebras which reflect the screening of the Coulomb hole. This opens new perspectives for a symmetry-based understanding of how the periodic law emerges from its quantum mechanical foundations, and holds the future promise of complementing our current phenomenological approach by a direct atomic physics approach. (shrink)

The general chemistry curriculum includes a prelude that consumes nearly all of the first semester and occupies the first third of the typical textbook. This necessary prelude to the main event is comparable in scope to precalculus though not broken out as a formal ‘prechemistry’ course. Atomic orbitals account for much of this prelude-to-chemistry. By tradition, orbital theory is conveyed to the student in three disjunct pieces, presented in the following illogical order: the Pauli principle, the Aufbau principle, and Hund’s (...) rule. (Often the n + l rule is tossed into the mix as well, though with no fixed place in the scheme). In the early twentieth century, as various researchers announced new insights into the atom at unpredictable intervals, no one could have been faulted for teaching orbitals in such a manner, catch-as-catch-can. A hundred years on, the vestiges of that (presumed) practice look wrong, and are indefensible. In the approach advocated here, orbitals would be taught as a single hierarchical rule-set, with the parts coherently sequenced as Aufbau–Hund–Pauli (and with Madelung’s n + l rule rehabilitated as part of Aufbau, no longer a free-floating mnemonic aid only). Logic aside, pragmatism offers its own argument for adopting this scheme: A tighter approach to Aufbau can lighten the ‘prechemistry’ burden significantly and bring the student that much sooner to chemistry itself. (shrink)

Summary Linus Pauling played a key role in creating valence-bond theory, one of two competing theories of the chemical bond that appeared in the first half of the 20th century. While the chemical community preferred his theory over molecular-orbital theory for a number of years, valence-bond theory began to fall into disuse during the 1950s. This shift in the chemical community's perception of Pauling's theory motivated Pauling to defend the theory, and he did so in a peculiar way. Rather than (...) publishing a defence of the full theory in leading journals of the day, Pauling published a defence of a particular model of the double bond predicted by the theory in a revised edition of his famous textbook, The Nature of the Chemical Bond. This paper explores that peculiar choice by considering both the circumstances that brought about the defence and the mathematical apparatus Pauling employed, using new discoveries from the Ava Helen and Linus Pauling Papers archive. (shrink)

Discussing the relationship of mathematics to chemistry is closely related to the emergence of physical chemistry and of quantum chemistry. We argue that, perhaps, the most significant issue that the 'mathematization of chemistry' has historically raised is not so much methodological, as it is philosophical: the discussion over the ontological status of theoretical entities which were introduced in the process. A systematic study of such an approach to the mathematization of chemistry may, perhaps, contribute to the realist/antirealist debate. To this (...) end, in this paper we briefly discuss Lewis' introduction of fugacity and activity to his chemical thermodynamics and more fully analyze the issues surrounding the appropriation of resonance by Linus Pauling into quantum chemistry, particularly as these issues arose in organic chemistry as discussed by George W. Wheland. (shrink)

This paper analyses Richard Bader’s ‘operational’ view of quantum mechanics and the role it plays in the the explanation of chemistry. I argue that QTAIM can partially be reconstructed as an ‘austere’ form of quantum mechanics, which is in turn committed to an eliminative concept of reduction that stems from Kemeny and Oppenheim. As a reductive theory in this sense, the theory fails. I conclude that QTAIM has both a regulatory and constructive function in the theories of chemistry.

This paper first queries what type of concept of emergence, if any, could be connected with the different chemical activities subsumed under the label ‘quantum chemistry’. In line with Roald Hoffmann, we propose a ‘rotation to research laboratory’ in order to point out how practitioners hold a molecular whole, its parts, and the surroundings together within their various methods when exploring chemical transformation. We then identify some requisite contents that a concept of emergence must incorporate in order to be coherent (...) from the standpoint of the scientific practices involved. In this respect, we finally propose a relational form of emergence which pays attention to the constitutive role of the modes of intervention and to the co-definition of the levels of organization. No metaphysical distinction between the higher and basic levels of organization is supposed, but only a plurality of modes of access. Moreover, these modes of access are not construed as mere ways of revealing intrinsic patterns of organization but, on the contrary, are considered to be active elements on which the constitution of those patterns depends. What is at stake in this paper is therefore not an ontological form of emergence but an agnostic one which fits what chemists do in their daily work. (shrink)

Recently, the author of this paper and his research team have extended the orthodox quantum theory of atoms in molecules (QTAIM) to a novel paradigm called the two-component QTAIM (TC-QTAIM). This extended framework enables one to incorporate nuclear dynamics into the AIM analysis as well as performing AIM analysis of the exotic species; positronic and muonic species are a few examples. In present paper, this framework has been reviewed, providing some computational examples with particular emphasis on origins and applications, in (...) a non-technical language. The main questions, enigmas and basic ideas that finally yielded the TC-QTAIM are considered in chronological order to help the reader comprehend the intuition behind the math. Finally, it is demonstrated that the TC-QTAIM and its more refined versions are able to tackle problems inaccessible to the orthodox QTAIM. (shrink)

In Neither Physics Nor Chemistry, Kostas Gavroglu and Ana Simoes examine the evolution of quantum chemistry into an autonomous discipline, tracing its development from the publication of early papers in the 1920s to the dramatic changes ...

After Heitler and London published their pioneering work on the application of quantum mechanics to chemistry in 1927, it became an almost unquestioned dogma that chemistry would soon disappear as a discipline of its own rights. Reductionism felt victorious in the hope of analytically describing the chemical bond and the structure of molecules. The old quantum theory has already produced a widely applied model for the structure of atoms and the explanation of the periodic system. This paper will show two (...) examples of the entry of quantum physics into more classical fields of chemistry: inorganic chemistry and physical chemistry. Due to their professional networking, George Hevesy and Michael Polanyi found their ways to Niels Bohr and Fritz London, respectively, to cooperate in solving together some problems of classical chemistry. Their works on rare earth elements and adsorption theory throws light to the application of quantum physics outside the reductionist areas. They support the heuristic and persuasive value of quantum thinking in the 1920–1930s. Looking at Polanyi’s later oeuvre, his experience with adsorption theory could be a starting point of his non-justificationist philosophy. (shrink)

In his classic work The Mind and its Place in Nature published in 1925 at the height of the development of quantum mechanics but several years after the chemists Lewis and Langmuir had already laid the foundations of the modern theory of valence with the introduction of the covalent bond, the analytic philosopher C. D. Broad argued for the emancipation of chemistry from the crass physicalism that led physicists then and later—with support from a rabblement of philosophers who knew as (...) much about chemistry as etymologists—to believe that chemistry reduced to physics. Here Broad’s thesis is recast in terms more familiar to chemists. In the hard sell of particle physics, several prominent figures in chemistry—Hoffmann, Primas, and Pauling—have had their views interpreted to imply that they were sympathetic to greedy reductionism when in fact they were not. Indeed, being chemists without physicists as alter egos, they could not but side with Broad’s contention that chemistry, as a science that deals primarily in emergent phenomena which are beyond the purview of physicalism, owes no acquiescence to particle physics and its ethereal wares. Historically, among the most widely used expediencies in chemistry and materials science are additivity or mixture rules and their cohort transferability, all of which are devised and used under the mantle of naive reductionism. Here it is argued that while the transfer of functional groups between molecules works empirically to an extent, it is strictly outlawed by the no-cloning theorem of quantum mechanics. Several illustrative examples related to chemistry’s irreducibility to physics are presented and discussed. The failure of naive reductionism exhibited by the deep-inelastic scattering of leptons by A > 2 nuclei is traced to the same flawed reasoning that was the original basis of Moffitt’s ‘atoms in molecules’ hypothesis, the neglect of context, nuclei in the case of high-energy physics and molecules in the case of chemistry. A non-exhaustive list of other contexts from physics, chemistry, and molecular biology evidencing similar departures from the ideal of additivity or reductionism is provided for the perusal of philosophers. Had the call by the mathematician J. T. Schwartz for developments in mathematical linguistics possessed of a less single, less literal, and less simple-minded nature been met, perhaps it might have persuaded scientists to abandon their regressive fixation with unphysical reductionism and to adapt to new methodologies that engender a more nuanced handling of ubiquitous emergent phenomena as they arise in Nature than is the case today. (shrink)

A lively philosophical debate has lately arisen over the nature of elementhood in chemistry. Two different senses in which the technical term ELEMENT is currently in use by chemists have been identified, leaving chemistry open to the logical fallacy of equivocation. This paper introduces a third, more elemental candidate: the high-enthalpy short-lived unbonded atom. An enthalpy index based on free-atoms-as-elements is established, whereby one can monitor the degree to which an atom’s spin-based attractive force is implemented exo-enthalpically when the atom (...) binds chemically to others. Enthalpy indexing shows that the strength of an atom’s attractive force is proportional to its spin angular momentum. Vibrational spectroscopy shows that the force varies inversely as the fourth power of the inter-atom distance. Both features differentiate the chemical force from the stronger electromagnetic force and from the weaker Van der Waals force. (shrink)

In this paper we will address the problem of the existence of orbitals by analyzing the relationship between molecular chemistry and quantum mechanics. In particular, we will consider the concept of orbital in the light of the arguments that deny its referring character. On this basis, we will conclude that the claim that orbitals do not exist relies on a metaphysical reductionism which, if consistently sustained, would lead to consequences clashing with the effective practice of science in its different branches.

Mulliken proposed an Aufbauprinzip for the molecules on the basis of molecular spectroscopy while establishing, point by point, his concept of molecular orbit. It is the concept of electronic state which becomes the lever for his attribution of electronic configurations to a molecule. In 1932, the concept of orbit was transmuted into that of the molecular orbital to integrate the probabilistic approach of Born and to achieve quantitative accuracy. On the basis of the quantum works of Hund, Wigner, Lennard-Jones and (...) group theory, he suggested the fragment method to establish the characteristics of molecular orbital for polyatomic molecules. These developments make it possible to bring elements of thought on the relation between a molecular whole and its parts . An operational realism combined with the second law of thermodynamics can pave the way for interesting tracks in the mereological study of chemical systems. (shrink)

In this paper I expand Eric Scerri’s notion of Popper’s naturalised approach to reduction in chemistry and investigate what its consequences might be. I will argue that Popper’s naturalised approach to reduction has a number of interesting consequences when applied to the reduction of chemistry to physics. One of them is that it prompts us to look at a ‘bootstrap’ approach to quantum chemistry, which is based on specific quantum theoretical theorems and practical considerations that turn quantum ‘theory’ into quantum (...) ‘chemistry’ proper. This approach allows us to investigate some of the principles that drive theory formation in quantum chemistry. These ‘enabling theorems’ place certain limits on the explanatory latitude enjoyed by quantum chemists, and form a first step into establishing the relationship between chemistry and physics in more detail. (shrink)

Since Mendeleev’s discovery in 1869, the periodic table has figured as the ultimate paper tool in chemical research. It has proved to be a vital research instrument in the arsenal of the chemical community. No chemistry textbook, lecture theatre or scientific laboratory is complete without a copy of the periodic table of the elements. -/- This however, should not necessarily imply that the periodic table has never had to contend with problems. In this thesis, the history of the accommodation of (...) the rare-earth elements in the periodic table will be addressed. When Mendeleev published his periodic table in 1869, the rare earths already constituted a major obstacle. Mendeleev was able to include only four members of the rare earths and he experienced great difficulties in positioning these elements. Question marks and wrong atomic weights reigned in the last rows of Mendeleev’s system. -/- This problematic accommodation quickly grew into one of the most serious threats for the periodic law. For over fifty years, chemists continually struggled with the placement of these maddeningly similar elements. As a consequence, a lot of chemists started to question the validity of the periodic law, but others took it as a sign that the concept of a chemical element had to be reconsidered. As a result, this work intends to retrace the mutual influence of the philosophical ideas about the nature of chemical elements and the development of the periodic table from its inception in 1869 to the discovery of Moseley’s law in 1913 and Bohr’s publication of his landmark paper On the Constitution of Atoms and Molecules. -/- The aim of this thesis is to show how, on the one hand, the periodic table (as a research instrument) helped in reformulating the contemporary ideas about chemical elements, and how it aided in developing a new research program in order to resolve the rare earth crisis. On the other hand, the question will be taken up to what extent Crookes’ evolutionary ideas about meta elements helped in saving the periodic table from a severe downfall by solving the gnawing problem of the rare-earth elements. In particular, this work will also focus on the investigations of the Czech chemist, Bohuslav Brauner. It will be shown how Brauner, under the influence of Crookes’ ideas, was led to his formulation of the Asteroid Hypothesis, according to which all the rare-earth elements should be placed in a single case of the periodic table. (shrink)

Because most chemical reactions, by definition, cannot avoid breaking of bonds, weakly bonded species exist fleetingly in almost every chemical change. Historically, chemical quantum mechanics was aimed at explaining the nature of strong bonds. The theory involved a number of approximations to the full solution of the Schrödinger equation. The study of non‐Kekulé molecules provides an opportunity to test whether modern quantum chemical computations are competent to deal with the nature of molecules with very weak bonds. †To contact the author, (...) please write to: Department of Chemistry, Yale University, New Haven, CT: 06520‐8107; e‐mail: [email protected] (shrink)

This note is intended to address one particular issue in the relative status of Quantum Chemistry in comparison to both Chemistry and Physics. It has been suggested, in the context of the question of the reduction relations between Chemistry and Physics that Quantum Chemistry as a research programme is incapable of furnishing useful guidance to practising chemists. If true, this claim will let us qualify Quantum Chemistry as a degenerating research programme, which, due to its complexity has difficulty to be (...) applied to Chemistry. This claim is shown to be false. The replacement claim I wish to make is that Quantum Chemistry is perfectly capable of furnishing such guidance, but renders the ontological status of many models favored by chemists problematic. Quantum Chemistry, however, validates these models in an instrumental fashion. I will argue that Quantum Chemistry is a progressive research programme. (shrink)

I claim that the question of whether chemistry is reduced to quantum mechanics is more ambiguous and multi-faceted than generally supposed. For example, chemistry appears to be both reduced and not reduced at the same time depending on the perspective that one adopts. Similarly, I argue that some conceptual issues in quantum mechanics are ambiguous and can only be laid to rest by embracing paradox and ambiguity rather than regarding them as obstacles to be overcome. Recent work in the reduction (...) of chemistry is also reviewed, including discussions of the ontological reduction of chemistry and the question of the emergence of chemistry from physics. (shrink)

This commentary provides a critical examination of a recent article by Allen and Knight in which the authors claim to provide the long-sought explanation for the Madelung, or n + ℓ, n rule for the order of orbital filling in many-electron atoms. It is concluded that the explanation is inadequate for several reasons.

Periodic tables (PTs) are the ‘ultimate paper tools’ of general and inorganic chemistry. There are three fields of open questions concerning the relation between PTs and physics: (i) the relation between the chemical facts and the concept of a periodic system (PS) of chemical elements (CEs) as represented by PTs; (ii) the internal structure of the PS; (iii)␣The relation between the PS and atomistic quantum chemistry. The main open questions refer to (i). The fuzziness of the concepts of chemical properties (...) and of chemical similarities of the CE and their compounds guarantees the autonomy of chemistry. We distinguish between CEs, Elemental Stuffs and Elemental Atoms. We comment on the basic properties of the basic elements. Concerning (ii), two sharp physical numbers (nuclear charge and number of valence electrons) and two coarse fuzzy ranges (ranges of energies and of spatial extensions of the atomic orbitals, AOs) characterize the atoms of the CEs and determine the two-dimensional structure of the PS. Concerning (iii), some relevant ‘facts’ about and from quantum chemistry are reviewed and compared with common ‘textbook facts’. What counts in chemistry is the whole set of nondiffuse orbitals in low-energy average configurations of chemically bonded atoms. Decisive for the periodicity are the energy gaps between the core and valence shells. Diffuse Rydberg orbitals and minute spin–orbit splittings are important in spectroscopy and for philosophers, but less so in chemical science and for the PS. (shrink)

The "usual story" regarding molecular chemistry is that it is roughly an application of quantum mechanics. That is to say, quantum mechanics supplies everything necessary and sufficient, both ontologically and epistemologically, to reduce molecular chemistry to quantum mechanics. This is a reductive story, to be sure, but a key explanatory element of molecular chemistry, namely molecular structure, is absent from the quantum realm. On the other hand, typical characterizations of emergence, such as the unpredictability or inexplicability of molecular structure based (...) on quantum mechanics, do not characterize the relationship between molecular chemistry and quantum mechanics well either. A different scheme for characterizing reduction and emergence is proposed that accommodates the relationship between quantum mechanics and molecular chemistry and some initial objections to the scheme are considered. (shrink)

The recent exchange on the quantum justification of the Periodic System of the Elements in this Journal between Scerri [Foundations of Chemistry 6: 93–116, 2004] and Friedrich [Foundations of Chemistry 6: 117–132, 2004] is supplemented by some methodological comments.

In this paper I investigate two views of theoretical explanation in quantum chemistry, advocated by John Clarke Slater and Charles Coulson. Slater argued for quantum‐mechanical rigor, and the primacy of fundamental principles in models of chemical bonding. Coulson emphasized systematic explanatory power within chemistry, and continuity with existing chemical explanations. I relate these views to the epistemic contexts of their disciplines.