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 ...

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.

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)

In this paper we will discuss some of the issues related to the attempts of Ralph Howard Fowler and Nevil Vincent Sidgwick to create a legitimizing space for quantum and theoretical chemistry in Britain. Although neither Fowler nor Sidgwick made original contributions to quantum chemistry, they followed closely the developments in the discipline, participated in meetings and discussions and delivered lectures, talks and addresses, where methodological topics, ontological questions and implicitly the problem of autonomy of the (...) new discipline vis-à-vis both physics and chemistry were taken to be pressing issues. In particular, they encouraged young people to work within the nascent discipline. Viewing quantum chemistry as a branch of applied mathematics became an emblematic characteristic of the practice of the new discipline in Great Britain. (shrink)

The incompatibility within the context of modeling cannot be established simpliciter. The fact that modeling is understood as an activity whose representational power can only be partially established, may minimize the supposed existence of incompatible models. Indeed, it is argued from perspectivism that incompatibility can be dissolved, meaning that it becomes trivial or simply false due to the inherently pragmatic and partial nature of the act of representation and modeling. From this perspective, incompatibility can only be a consequence of a (...) misunderstanding of the very nature of modeling and representation In this sense, in order to tackle this strategy at its root from perspectivism, we will first need to outline the maximal perspectivism thesis, attempting to identify the possible escape routes that perspectivism could find in order to explain incompatibility as an illusory incompatibility. Then, we will analyze Valence Bond Model and Molecular Model of covalent bonds, and we will conclude that the dissuasive strategies used to minimize and/or disregard incompatibility prove to be fruitless. (shrink)

In this contribution, the role of epistemology in understanding quantum chemistry is discussed. Quantum chemistry is the study of the behavior of atoms and molecules using the principles of quantum mechanics. Epistemology helps us evaluate claims to knowledge, distinguish between justified and unjustified beliefs, and assess the reliability of scientific methods. In quantum chemistry, the epistemology of knowledge is heavily influenced by the mathematical nature of quantum mechanics, and models can be tested, (...) proven, and validated through experimentation. This paper also discusses key concepts used in quantum chemistry, such as the wave-particle duality of matter and the uncertainty principle. This work utilizes Kant’s philosophy of science to frame debates and discussions in quantum chemistry, particularly with regard to the interplay between empirical observation and theory. Additionally, the text explores how Kant’s ideas about the role of the mind in constructing our understanding of the world can help us comprehend the counterintuitive phenomena of quantum mechanics and its applications in quantum chemistry theory. (shrink)

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

This article describes a descriptive-qualitative method for analyzing and reviewing several textbooks for high school as samples commonly used by teachers and students in their teaching–learning to reveal possible misconceptions. This study focused on the subjects of quantum numbers and electronic configuration. From the advanced literature review to analyze the samples the occurrence of various misconceptions was noted. All textbooks described correctly the four symbols of quantum numbers, but none correlates correctly the magnetic-angular quantum number to the (...) Cartesian labeled orbitals. All textbooks consider mistakenly the meaning of aufbau as the building-up energy of orbitals by following (n + ℓ, n) rules on describing the electronic configuration for all atoms. Only one textbook states that the electronic configuration of transition metal atoms (3d series) can be described in the following order of shell (n), thus giving rise to two types of electronic configurations, [Ar] 3d 4s (Type I) beside [Ar] 4s 3d (Type II), leading further misconception. All textbooks described favorably an unpaired electron of ms = + ½ due to the specific agreement, which is a potential misconception in applying Hund’s rule. In drawing the diagram boxes of orbitals, they are arranged in increasing or decreasing the numeric mℓ, due to the specific agreement, and again leading to a potential misconception on describing the quantum number of electrons issued. Three textbooks introduced the terms of the last and the xth electron associated with the quantum numbers, leading to serious further misconceptions. No books stated that the ordering energy of the (n + ℓ, n) rule is true only for the first twenty atoms. (shrink)

All suggested notions of reduction of two scientific theories are critically reviewed and analyzed. In particular those applied to the case of the alleged reduction of Chemistry to Quantum mechanics are examined. Since it is recognized that the weakness of this field of research is the lack of a definition of a scientific theory, it is suggested that a scientific theory is characterized by two choices regarding two dichotomies, that is, the kind of mathematics and the kind of (...) logic. According to this view a reduction is only possible between two theories in which the same choices are shared. As a consequence, only one case of reduction in the history of physics is recognized: physical optics to electromagnetism, a case that is commonly accepted. The other cases of claimed reductions are recognized as impossible, owing to the different choices of the two theories at issue and hence the radical variations in meaning of their shared basic notions. In particular, the claimed reduction of Chemistry to Quantum mechanics is disproved in detail. (shrink)

During the second half of the nineteenth century, electronegativity has been one of the most relevant chemical concepts to explain the relationships between chemical substances and their possible reactions. Specifically, EN is a property of the substances that allows them to attract external electrons in bonding situations. The problem arises because EN cannot be measured directly. Indeed, the only way to measure it is through different properties that do can be directly measured, for instance enthalpy, ionization energies or electron affinities. (...) What is particularly troubling about this case in quantum chemistry is that the different models used to describe and quantify EN are incompatible but, in a certain sense, equivalent because the same EN scale results in all of them. By analyzing Linus Pauling’s and Robert Mulliken’s models of EN, it will be argued that, if we remain cling to a traditional representative conception of models, we cannot understand the meaning of the information provided by those models. Indeed, if we do not want to adopt an instrumentalist point of view concerning chemical knowledge, we should reconsider by virtue of what a model represents the system, or, in other words, which the factors that determine the representative power of a model are. I will propose a new perspective that incorporates the role of experimental techniques in the very notion of representation; this perspective allows us to understand how supposedly incompatible models of the same target system can be both simultaneously representative. (shrink)

This book reflects on the significant and highly original scientific contributions of Hans Primas. A professor of chemistry at ETH Zurich from 1962 to 1995, Primas continued his research activities until his death in 2014. Over these 50 years and more, he worked on the foundations of nuclear magnetic resonance spectroscopy, contributed to a number of significant issues in theoretical chemistry, helped to clarify central topics in quantum theory and the philosophy of physics, suggested innovative ways of (...) addressing interlevel relations in the philosophy of science, and introduced cutting-edge approaches in the flourishing young field of scientific studies of consciousness. His work in these areas of research and its continuing impact is described by noted experts, colleagues, and collaborators of Primas. All authors contextualize their contributions to facilitate the mutual dialog between these fields. (shrink)

Along with exploring some of the necessary conditions for the chemistry of our world given what we know about quantum mechanics, I will also discuss a different reductionist challenge than is usually considered in debates on the relationship of chemistry to physics. Contrary to popular belief, classical physics does not have a reductive relationship to quantum mechanics and some of the reasons why reduction fails between classical and quantum physics are the same as for why (...) reduction fails between chemistry and quantum physics. However, a neoreductionist can accept that classical physics has some amount of autonomy from quantum mechanics, but still try to maintain that classical+quantum physics taken as a whole reduces chemistry to physics. I will explore some of the obstacles lying in the neoreductionist’s path with respect to quantum chemistry and thereby hope to shed more light on the conditions necessary for the chemistry of our world. (shrink)

A personal account is presented for the present status of mathematical chemistry, with emphasis on non-numerical applications. These use mainly graph-theoretical concepts. Most computational chemical applications involve quantum chemistry and are therefore largely reducible to physics, while discrete mathematical applications often do not. A survey is provided for opinions and definitions of mathematical chemistry, and then for journals, books and book series, as well as symposia of mathematical chemistry.

It is argued that the conventional descriptions of chemical bonds as covalent, ionic, metallic, and Van der Waals are compromising the usefulness of quantum mechanics in the synthesis and design of new molecules and materials. Parallels are drawn between the state of chemistry now and when the idea that phlogiston was an element impeded the development of chemistry. Overcoming the current obstacles will require new methods to describe molecular structure and bonding, just as new concepts were needed (...) before the phlogiston theory could be set aside. (shrink)

Recent publications by several leading philosophers of chemistry have focused on the definition, scope, utility, and nomenclature of issues dealing with acidity and basicity. In this paper, molecular orbital theory is used to explain all acid–base reactions, concluding that the interaction of the highest occupied molecular orbital (HOMO) of one substrate, “the base,” with the lowest unoccupied molecular orbital (LUMO) of a second substrate, “the acid,” determines the reactivity of such systems. This paradigm provides an understanding of all acid–base (...) reactions as well as other reactions which, on the surface, may not seem like acid–base reactions but which have fundamental underpinnings of that kind of chemistry. Rather than being unable to determine a unified understanding of acidity and basicity as suggested in the philosophy of chemistry literature, we propose that acidity and basicity fit securely in a classification of many other reactions that, using classical chemistry knowledge, pre-quantum chemistry, would not be possible. We strongly support the use of all scientific knowledge and experience in the development of the ideas in the philosophy science. We further suggest increased interactions between philosophers of science and scientists, so that all scholars benefit from the values, knowledge, and perspectives of other disciplines. (shrink)

Previous research in the history of physics has led us to believe that Yoshio Nishina (1890–1951) virtually single‐handedly imported quantum physics into Japan. However, there are first‐hand accounts that Yoshikatsu Sugiura (1895–1960) also played an important role. Sugiura made his name in quantum chemistry with his contribution to the Heitler‐London theory of the chemical bond. Yet, historians of physics have paid scant attention to him. This paper brings forward information on Sugiura from his letters, his scientific papers, (...) and his own recollections until ca. 1930. By examining this material, the present paper studies Sugiura's accomplishments in Europe and his contributions to the development of quantum physics in Japan. We conclude that Sugiura was one of the most important physicists when it comes to the arrival of quantum physics in Japan. In addition, we assess why he has been under‐appreciated in the history of physics in Japan. Our historical study on Sugiura suggests that, in addition to the position Nishina and his students rightfully occupy, there still are important unexplored aspects in the history of Japanese quantum physics. (shrink)

A quarter of a century has elapsed since quantum mechanics was discovered. Perhaps it is not too much to say, in retrospect, that the time was ripe for this particular development. This is attested, not only by the speed with which the edifice of the theory was completed immediately following the basic discoveries of Heisenberg and Schrödinger, but also by the rapidity, well-nigh unprecedented in the history of science with which the new results were applied to almost every branch (...) of physics and chemistry. A mental readiness on the part of the scientists involved might have had much more to do with this than the facilities of modern communication systems. (shrink)

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)

Strong claims have been made for emergence as a new paradigm for understanding science, consciousness, and religion. Tracing the past history and current definitions of the concept, Clayton assesses the case for emergent phenomena in the natural world and their significance for philosophy and theology. Complex emergent phenomena require irreducible levels of explanation in physics, chemistry and biology. This pattern of emergence suggests a new approach to the problem of consciousness, which is neither reducible to brain states nor proof (...) of a mental substance or soul. Although emergence does not entail classical theism, it is compatible with a variety of religious positions. Clayton concludes with a defence of emergentist panentheism and a Christian constructive theology consistent with the new sciences of emergence. (shrink)

These lecture notes present a concise and introductory, yet as far as possible coherent, view of the main formalizations of quantum mechanics and of quantum field theories, their interrelations and their theoretical foundations. The "standard" formulation of quantum mechanics (involving the Hilbert space of pure states, self-adjoint operators as physical observables, and the probabilistic interpretation given by the Born rule) on one hand, and the path integral and functional integral representations of probabilities amplitudes on the other, are (...) the standard tools used in most applications of quantum theory in physics and chemistry. Yet, other mathematical representations of quantum mechanics sometimes allow better comprehension and justification of quantum theory. This text focuses on two of such representations: the algebraic formulation of quantum mechanics and the "quantum logic" approach. Last but not least, some emphasis will also be put on understanding the relation between quantum physics and special relativity through their common roots - causality, locality and reversibility, as well as on the relation between quantum theory, information theory, correlations and measurements, and quantum gravity. Quantum mechanics is probably the most successful physical theory ever proposed and despite huge experimental and technical progresses in over almost a century, it has never been seriously challenged by experiments. In addition, quantum information science ha s become an important and very active field in recent decades, further enriching the many facets of quantum physics. Yet, there is a strong revival of the discussions about the principles of quantum mechanics and its seemingly paradoxical aspects: sometimes the theory is portrayed as the unchallenged and dominant paradigm of modern physical sciences and technologies while sometimes it is considered a still mysterious and poorly understood theory, waiting for a revolution. This volume, addressing graduate students and seasoned researchers alike, aims to contribute to the reconciliation of these two facets of quantum mechanics. (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 his book, 'History as a Science and the System of the Sciences', Thomas Seebohm articulates the view that history can serve to mediate between the sciences of explanation and the sciences of interpretation, that is, between the natural sciences and the human sciences. Among other things, Seebohm analyzes history from a phenomenological perspective to reveal the material foundations of the historical human sciences in the lifeworld. As a preliminary to his analyses, Seebohm examines the formal and material presuppositions of (...) phenomenological epistemology, as well as the emergence of the human sciences and the traditional distinctions and divisions that are made between the natural and the human sciences. -/- As part of this examination, Seebohm devotes a section to discussing Husserl’s formal mereology because he understands that a reflective analysis of the foundations of the historical sciences requires a reflective analysis of the objects of the historical sciences, that is, of concrete organic wholes (i.e., social groups) and of their parts. Seebohm concludes that Husserl’s mereological ontology needs to be altered with regard to the historical sciences because the relations between organic wholes and their parts are not summative relations. Seebohm’s conclusion is relevant for the issue of the reducibility of organic wholes such as social groups to their parts and for the issue of the reducibility of the historical sciences to the lower-order sciences, that is, to the sciences concerned with lower-order ontologies. -/- In this paper, I propose to extend Seebohm’s conclusion to the ontology of chemical wholes as object of quantum chemistry and to argue that Husserl’s formal mereology is descriptively inadequate for this regional ontology as well. This may seem surprising at first, since the objects studied by quantum chemists are not organic wholes. However, my discussion of atoms and molecules as they are understood in quantum chemistry will show that Husserl’s classical summative and extensional mereology does not accurately capture the relations between chemical wholes and their parts. This conclusion is relevant for the question of the reducibility of chemical wholes to their parts and of the reducibility of chemistry to physics, issues that have been of central importance within the philosophy of chemistry for the past several decades. (shrink)

In a recent article entitled “The problem of molecular structure just is the measurement problem”, Alexander Franklin and Vanessa Seifert argue that insofar as the quantum measurement problem is solved, the problems of molecular structure are resolved as well. The purpose of the present article is to show that such a claim is too optimistic. Although the solution of the quantum measurement problem is relevant to how the problem of molecular structure is faced, such a solution is not (...) sufficient to account for the structure of molecules as understood in the field of chemistry. (shrink)

In modern German ‘Anschauung’ is translated as intuition. But in Kant’s technical philosophical context, it means an intuition derived from previous visualizations of physical processes in the world of perceptions. The nineteenth century chemists’ predilection for Kantian Anschauung led them to develop an intuitive representation of what exists beyond the bounds of the senses. Molecular structure is one of the illuminating outcomes. (Ochiai 2021, pp. 1–51) This mental habit seems to be dominant among chemists even in the twentieth century, as (...) is illustrated by the electronic theory of organic chemistry and the frontier orbital theory as well. The former assumes that (1) bonds are paired electrons shared by bonded atoms—in fact, electrons in molecules are not localized in bonds; (2) the difference of electronegativities between bonded atoms causes electron drifts—expressed by the curly arrow—that result in bond formation or bond cleavage. The latter focuses on the orbitals that make the greatest contribution to the energy of a system undergoing electron delocalization, while the LCAO method says, as is suggested by the word Linear Combination of Atomic Orbitals, molecular orbitals should be constructed from all of the atomic orbitals that have the appropriate symmetry. In other words, every molecular orbital contributes to some extent to the electronic state of a molecule. The curly arrow in the electronic theory and the orbital lobe in the frontier orbital theory illustrate an intuitive character of these theories. Although both theories rely on such simple and qualitative models rather than mathematically rigid quantum mechanical calculations, they are successful in explaining, predicting, and designing chemical reactions. What makes these prima facie intuitive theories so successful? In this study we address this problem from a historical and philosophical as well as scientific point of view. The key to solve this problem is that they are concerned with only bond formation or bond cleavage, in which the localized-bond principle holds. (shrink)

Intra-molecular connectivity (that is, chemical structure) does not emerge from computations based on fundamental quantum-mechanical principles. In order to compute molecular electronic energies (of C 3 H 4 hydrocarbons, for instance) quantum chemists must insert intra-molecular connectivity “by hand.” Some take this as an indication that chemistry cannot be reduced to physics: others consider it as evidence that quantum chemistry needs new logical foundations. Such discussions are generally synchronic rather than diachronic —that is, they neglect (...) ‘historical’ aspects. However, systems of interest to chemists generally are metastable . In many cases chemical systems of a given elemental composition may exist in any one of several different metastable states depending on the history of the system. Molecular structure generally depends on contingent historical circumstances of synthesis and separation, rather than solely or mainly on relative energies of alternative stable states, those energies in turn determined by relationships among components. Chemical structure is usually ‘kinetically-determined’ rather than ‘thermodynamically-determined.’ For instance, cyclical hydrocarbon ring-systems (as in cyclopropene) are produced only in special circumstances. Adequate theoretical treatments must take account of the persistent effects of such contingent historical events whenever they are relevant—as they generally are in chemistry. (shrink)

Atomic states are rigorously characterized by the total orbital angular momentum and the total spin angular momentum, but chemists persist in the use of electron configurations based on one-electron quantum numbers and simplified rules for predicting ground state configurations. This practice is defended against two lines of criticism, and its use in teaching chemistry is encouraged with the claim that the inductive approach of Mendeleev and the deductive approach initiated by Schrödinger compose the consummate example of that interaction (...) of empirical and rational epistemologies that defines how chemists think. (shrink)

J. Quantum Chemistry, 2000"It will have a lasting value for theoretical chemists and science historians".Structural Chemistry, 2000" is a finely produced, ...

It is with great delight that I have accepted the unexpected invitation to edit this two part special issue of Foundations of Chemistry dedicated to the philosophical aspects and implications of the quantum theory of atoms in molecules (QTAIM) (Bader 1990). This theory has been primarily the oeuvre of Richard F. W. Bader (1931–2012), one of his most significant (but not the only significant) contributions to chemistry. Bader’s contributions have been summarized in a tribute (Matta et al. (...) 2011) that appeared in a recent Festschrift of The Journal of Physical Chemistry A (2011). This special issue of Foundations is neither a duplication, a complement, or an afterthought to that Festchrift, nor is it intended as another tribute to this great scientist, as deserving as he may be, instead it serves an entirely different purpose. This issue is focused principally on the epistemology and ontology of the science of QTAIM. The sort of questions that are addressed in, or that should emerge from. (shrink)

In this essay I consider whether the theory of organic chemistry is reducible to the theory of quantum chemistry. Using philosophical machinery developed by James Woodward, I characterize the understanding provided by both theories. Then I argue that there are systematic reasons to suspect that quantum chemistry is incapable of supporting some of the significant explanations, predictions, and applications underwritten by an understanding of theoretical organic chemistry. Consequently, even should quantum chemistry be (...) ‘reducible to’ quantum physics in some suitable sense, there are good reasons to doubt that many of the significant results of organic chemistry could be reproduced by quantum chemistry alone. (shrink)

The modal-Hamiltonian interpretation belongs to the modal family of interpretations of quantum mechanics. By endowing the Hamiltonian with the role of selecting the subset of the definite-valued observables of the system, it accounts for ideal and non-ideal measurements, and also supplies a criterion to distinguish between reliable and non-reliable measurements in the non-ideal case. It can be reformulated in an explicitly invariant form, in terms of the Casimir operators of the Galilean group, and the compatibility of the MHI with (...) the theory of decoherence has been proved. Nevertheless, perhaps its main advantage in the eyes of a scientist is given by its several applications to well-known physical situations, leading to results compatible with experimental evidence. The purpose of this paper is to add a new application to the list: the case of optical isomerism, which is a central issue for the philosophy of physics and of chemistry since it points to the core of the problem of the relationship between physics and chemistry. Here it will be shown that the MHI supplies a direct and physically natural solution to the problem, a solution that does not require putting classical assumptions in “by hand.”. (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)

In this paper, aspects of observable and non-observable based models are discussed. A survey of recent literature was done to show how using non-observable-based language carelessly may cause disagreement, even in professional research programs and incorrect assertions, even in prestigious journals. The relation between physical measurements and observables is discussed and it is shown that, in contrast to general belief, this relation may be complicated and not always straightforward. The decomposition of the system into basic subsystems (physical or conceptual) is (...) traced as the origin of non-observable-based languages. The possibility of defining new quantum mechanical observables for open quantum subsystems and of replacing them with non-observable-based concepts has been mentioned and the AIM theory is explained as an example. An account of some current non-observable-based models for molecular geometry is discussed and it is shown that not all non-observable-based languages possess the same effectiveness. In the end, the need to develop a clear chemical language is stressed. (shrink)

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)

This paper traces the origins of Eugene Wigner's pioneering application of group theory to quantum physics to his early work in chemistry and crystallography. In the early 1920s, crystallography was the only discipline in which symmetry groups were routinely used. Wigner's early training in chemistry, and his work in crystallography with Herman Mark and Karl Weissenberg at the Kaiser Wilhelm institute for fiber research in Berlin exposed him to conceptual tools which were absent from the pedagogy available (...) to physicists for many years to come. This both enabled and pushed him to apply the group theoretic approach to quantum physics. It took many years for the approach first introduced by Wigner in the 1920s – and whose reception by the physicists was initially problematical – to assume the pivotal place it now holds in physical theory and education. This is but one example that attests to the historic contribution made by the periphery in initiating new types of thought-perspectives and scientific careers. (shrink)

In my previous article on the benzene problem, I described how Pauling's valence bond (resonance) theory, sometimes regarded as a modernized version of Kekule's oscillation hypothesis, came to be accepted by chemists by the end of World War II. But the alternative molecular orbital theory, proposed by Mulliken, had already been developed and was regarded as quantitatively superior by many quantum chemists, though it was not as easy to visualize and did not seem to harmonize as well with traditional (...) chemical concepts. During the 1950s and 1960s, thanks to the efforts of Charles Coulson and many other theorists, the molecular orbital approach not only dominated theoretical discussions but also started to be accepted by the chemical community as a whole and became the preferred description for benzene. Possible reasons were: its greater calculational convenience when applied to large molecules; better expository methods directed toward chemists; the spectacular success of the Woodward-Hoffmann rules for pericyclic reactions and Fukui's frontier orbital theory; and the development of a general theory of aromaticity, which predicted properties of similar molecules such as cyclobutadiene (C4H4). The relative importance of these reasons is explored through a mail survey of chemists. (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)