Table Of ContentSynthese Library 461
Studies in Epistemology, Logic, Methodology,
and Philosophy of Science
Olimpia Lombardi
Juan Camilo Martínez González
Sebastian Fortin Editors
Philosophical
Perspectives
in Quantum
Chemistry
Synthese Library
Studies in Epistemology, Logic, Methodology,
and Philosophy of Science
Volume 461
Editor-in-Chief
OtávioBueno,DepartmentofPhilosophy,UniversityofMiami,CoralGables,USA
EditorialBoardMembers
BeritBrogaard,UniversityofMiami,CoralGables,USA
AnjanChakravartty,DepartmentofPhilosophy,UniversityofMiami,CoralGables,
USA
StevenFrench,UniversityofLeeds,Leeds,UK
CatarinaDutilhNovaes,VUAmsterdam,Amsterdam,TheNetherlands
DarrellP.Rowbottom,DepartmentofPhilosophy,LingnanUniversity,TuenMun,
HongKong
Emma Ruttkamp, Department of Philosophy, University of South Africa, Pretoria,
SouthAfrica
Kristie Miller, Department of Philosophy, Centre for Time, University of Sydney,
Sydney,Australia
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Olimpia Lombardi
Juan Camilo Martínez González
Sebastian Fortin
Editors
Philosophical Perspectives
in Quantum Chemistry
Editors
OlimpiaLombardi JuanCamiloMartínezGonzález
UniversityofBuenosAiresandCONICET UniversityofBuenosAiresandCONICET
CiudaddeBuenosAires,Argentina CiudaddeBuenosAires,Argentina
SebastianFortin
CONICET,UniversidaddeBuenosAires
BuenosAires,Argentina
ISSN0166-6991 ISSN2542-8292 (electronic)
SyntheseLibrary
ISBN978-3-030-98372-7 ISBN978-3-030-98373-4 (eBook)
https://doi.org/10.1007/978-3-030-98373-4
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Preface
Working in philosophy of science is not easy when one lives in the southernmost
country of South America. Furthermore, the community of the philosophy and
foundations of chemistry is relatively small, and its members are scattered all over
the world. Fortunately, current technology has facilitated communication and has
madepossiblecertainprojectsthatwouldhavebeenunthinkableinpasttimes.This
volumeisoneofthoseprojects.
Thisvolumewasproducedduringveryhardtimes:thepandemichasturnedour
livesupsidedowninmanyways,andwehavehadtoadapttoasituationthatwillbe
remembered for a long time. In spite of this, today we are proud to present this
volume about the philosophy of quantum chemistry, which would not have been
possible without the effort and the commitment of all the authors who contributed
withtheirworkstothisproject.Ourspecialrecognitiongoestoallofthem.
Wewouldalsoliketorecallthesupportofthegroupofphilosophyofchemistry
led by Olimpia, which, although based in Buenos Aires, includes researchers and
students from other cities of Argentina: in addition to two of us, Juan Camilo
Martínez González and Sebastian Fortin, also Hernán Accorinti, Fiorela Alassia,
Jesús Jaimes Arriaga, and Alfio Zambon. Last, but not least, we would like to
express our gratitude to Springer, in particular to the Synthese Library Series in
the person of its editor-in-chief, Otávio Bueno, for his kind invitation to edit this
volumeinthecontextoftheseries,andtoitsProjectCoordinator,PalaniMurgesani,
forhispatienceandassistanceduringallthestagesofthisproject.
CiudaddeBuenosAires,Argentina OlimpiaLombardi
February2022 JuanCamiloMartínezGonzález
SebastianFortin
v
Introduction
At present, the philosophy of chemistry is a vigorous branch of the philosophy of
science, congregating researchers from all around the world. The International
SocietyforthePhilosophyofChemistry(ISPC),foundedin1997,sponsorsannual
meetings since its foundation, in which scholars share their research results and
discusscurrenttopicsofthearea.Thesubdisciplineisalsocoveredbytwospecial-
ized publications, Foundations of Chemistry (since 1999, official journal of the
ISPC), and Hyle–International Journal for Philosophy of Chemistry (since 1995).
Despite this intense activity, the philosophy of chemistry has consolidated very
recently when compared, for instance, with the philosophy of physics and the
philosophy of biology, a fact that contrasts with the long history of chemistry as a
scientific discipline. The question is what explains this relatively delayed
consolidation.
Although chemistry developed independently from physics until the end of
the nineteenth century, its independence began to be questioned since the advent
of quantum mechanics. The astonishing success of the quantum explanations
supportedthebeliefinthepossibilityofaccountingfor allchemicalphenomenain
physicalterms.Therefore,despitethescientificandmethodologicalpeculiaritiesof
the chemical sciences, the assumption of the reduction of chemistry to quantum
mechanics turned out to be a leitmotiv both in science and in philosophy. As a
consequence,duringmostpartofthetwentiethcentury,itwasalsoassumedthatthe
philosophical problems of chemistry were, when properly analyzed, problems for
thephilosophyofphysics.
In the face of this situation, it is not surprising that, when the philosophy of
chemistry was introduced in the philosophical thinking in the last decades of the
twentiethcentury,theproblemoftherelations betweenchemistry andphysicswas
oneofthehottesttopics.Severalauthors,comingfrombothphilosophyandchem-
istry,emphasizedtheneedtoadoptamorecarefulperspectivetocounteruncritical
assumptionsofreduction.Infact,manycasestudiesforphilosophicalreflectionhave
focused on concepts that inhabit the space between chemistry and physics. For
instance, Lewis’s theory of chemical bond, conceived as a pair of electrons shared
vii
viii Introduction
between atoms, was revised when approached from quantum physics: since elec-
trons are elemental quantum particles, they are indistinguishable in principle and,
consequently, cannot be identified in the constitution of a chemical bond. Another
centralconceptthatneededtobereconsideredinthelightofquantummechanicswas
molecular structure: whereas central for chemistry, the very notion of molecular
structure finds no comfortable place in the quantum context because quantum
particles cannot be conceived at rest in definite positions due to the Heisenberg
Principle;furthermore,theveryexistenceofisomersseemstobechallengedbythe
factthatquantumHamiltoniansdonotdistinguishbetweenthem.Butnotonlythis
kindofconceptsisrevisitedasquantummechanicsenteredthestage;eventhenature
oftheperiodictable,atheoretical constructthat liesattheveryheartofchemistry,
hasbeentheobjectofreneweddiscussions.Someauthorsbelievethatthetableisin
principle derivable from quantum physics, whereas others consider that chemical
elements,withtheirpeculiarmacroscopicproperties,cannotbereducedbutemerge
fromanunderlyingquantumdomain.
Althoughthesequestionsaboutthelinksbetweenchemistryandphysicsalready
constitute an important issue from a general viewpoint, they acquire a special
relevance in the particular context of quantum chemistry, a field which, from its
veryorigins,filledaproblematicpositioninthedisciplinaryspace.Ontheonehand,
quantum chemistry is a subdiscipline of chemistry, in particular, a branch of
theoretical chemistry. On the other hand, it appeals essentially to theoretical tools
coming from physics to obtain its results. This intermediate position, while raising
questions about its disciplinary identity, makes quantum chemistry a privileged
arena for discussing inter-theoretic and inter-disciplinary relationships. One of the
main approaches in quantum chemistry is the Density Functional Theory (DFT),
whose purpose is to compute the properties of many-electron systems – typically
molecules–bymeansoffunctionalsofthespatiallydependentelectronicdensity.In
this context, the Hohenberg-Kohn (HK) theorems play a central role: the first HK
theorem proves that the properties of a molecule in its ground state are uniquely
determined by the electron density; the second HK theorem proves that an energy
functional can be defined such that it is minimized by the ground-state electron
density.Theotherapproachisthequantumtheoryofatomsinmolecules(QTAIM),
whichaimsatdefiningchemicalbondingexclusivelyintermsofthetopologyofthe
electronicdensity:byidentifyingtopologicalatoms,obtainedbydividingspaceinto
volumescontainingonenucleusthatactsasanattractoroftheelectrondensity,the
theory offers a quantum mechanical view of the structure of molecules. Both
theoretical approaches, which combine an intensive use of quantum tools with
molecular chemistry knowledge, open up a new perspective for the analysis of the
manyandsubtlelinksbetweenchemistryandphysics.
In addition to the theoretical dimension, quantum chemistry leads us to rethink
ourphilosophicalpictureofscience,stronglyshapedontheimageofphysics.Infact,
from the outset, quantum chemistry begins to outline its identity, not around a
theoreticalbody,butasanactivitythatintegratestheoreticalelementsandmethod-
ologicalstrategiescomingfromchemistry,physics,mathematics,andinformatics.In
thiscontext,theappealtomodelsisnotonlypervasive,asinothersciences,butis
Introduction ix
also constitutive of the area as a scientific discipline. However, far from any
representationalist purpose, quantum-chemical models play an essentially
pragmatic role: they are used not only to predict chemical properties, but also to
designnewsubstances.Itisalsointhissensethattheidentityofquantumchemistry
isnotcommittedtoanyparticularontologicalreference,butratherreliesonabody
ofpracticessharedbyascientificcommunityofresearchersfromawidevarietyof
backgrounds.
Itisinthisbroadcontextofnewtheoretical,historical,andmethodologicalissues
that the question about the nature of quantum chemistry deserves to be considered
from a conceptual viewpoint. The aim of this volume is, precisely, to address the
subjectmatter from diverseperspectives, whichilluminate its different aspectsand
implications. With this purpose, the articles of the volume are organized into three
parts.
PartI,“QuantumChemistry:HistoryandPractices,”groupsfourchaptersmainly
devotedtoinquiringintotheverynatureofquantumchemistryfromhistoricaland
pragmatic viewpoints. This part opens with the chapter “Quantum Chemistry in
Historical Perspective,” in which Stylianos Kampouridis, Ana Simões, and
Theodore Arabatzis provide a detailed and informed historical account of how
quantumchemistrywasdevelopedbycrossingdisciplinaryfrontiersandintegrating
newinstruments.Bydiscussingconceptual,institutional,methodological,andepis-
temological matters, the authors show the path followed by quantum chemistry in
the development of its identity as an in-between/boundary discipline. The second
chapter, “How Chemical Is Quantum Chemistry?,” by Klaus Ruthenberg, also
adopts a historical perspective, but in this case to draw attention to the deep
breakdown between quantum chemistry and the macroscopic chemistry of sub-
stances. The main purpose of the author is to point to the danger of overlooking
thelimitationsofquantumchemistryinexplainingthebehaviorofsubstances,which
needmacro-chemicalpracticesforeigntoquantummechanics.Inthethirdchapter,
“Interacting Practices: Quantum Chemistry and Organic Synthesis,” William
Goodwin characterizes quantum chemistry as an interfield theory and focuses on
its contributions to synthetic organic chemistry, which is mainly concerned with
makingnovelcompounds.Basedonthisanalysis,theauthormovesawayfromthe
traditional hierarchical vision of the sciences and promotes a pluralistic vision, in
terms ofboth interestsandcognitivetools. Inthefourthand closing chapterofthe
first part, “The Elimination of the Holism-Reductionism Dichotomy Through the
AnalysisofQuantumChemistry,”Jean-Pierre Llored appealstotheeffectivecom-
putationalpracticeofquantumchemistrytoarguethattheusualholism-reductionism
dichotomy is superseded by that very practice: the different types of calculation
carried out in the field show not only the interdependence and codetermination of
parts and wholes,but also theessential role played by the environment inthe very
definitionofthesystemsunderstudy.
Part II, “Models in Quantum Chemistry,” is composed of two chapters that
analyze,from different perspectives, thecentralrole played byscientificmodels in
quantumchemistry.Thechapter“ModelsandIdealizationsinQuantumChemistry:
The Case of the Born-Oppenheimer Approximation,” by Juan Camilo Martínez
x Introduction
González andHernánAccorinti, isdevotedto analyzing different classificationsof
idealizations proposed in the philosophical literature. The aim of the authors is to
show that the Born-Oppenheimer approximation (which strictly speaking is not an
approximation but an idealization) cannot be comfortably subsumed under those
traditional schemes: it requires a refinement or enrichment of the existing classifi-
cations.Inthefollowingchapter,“DoMoleculesHaveStructureinIsolation?How
ModelsCanProvidetheAnswer,”VanessaA.Seifertdistinguishesbetweenmodels
of isolated molecules and models of molecules in interaction. The former need to
appeal to the Born-Oppenheimer approximation to identify molecular structure,
since without it, the isolated molecule has no structure; the latter do not need to
appeal to the Born-Oppenheimer approximation since non-isolated molecules can
acquire their structure as a consequence of being embedding into a surrounding
medium. These two chapters, although focusing on the use of models in quantum
chemistry,openthewaytothediscussionsofthethirdpartofthevolume.
Part III, “Quantum Chemistry and Quantum Mechanics,”with itsfour chapters,
tacklesdirectlytheissueoftheinter-theoryandinter-disciplinarylinksinvolvedin
quantum chemistry. In the first chapter of this part, “Quantum Mechanics and
Molecular Structure,” Robin Findlay Hendry examines the relationship between
quantummechanicsandthechemicalconceptsofmolecularstructureandchemical
bond.Onthisbasis,theauthorrejectsthereductionistapproach,accordingtowhich
physical facts ontologically determine all the chemical facts, and advances an
emergentist view of that relationship, since it is better aligned with the role of
quantum mechanics in chemistry. The following chapter, “Is Chemistry Really
Founded in Quantum Mechanics?,” by Brian Sutcliffe and R. Guy Woolley, is a
verydetailedandscientificallyinformeddiscussionofthesubtletiesinvolvedinthe
useof quantummechanics intheoretical chemistry. The authorsstress that evenin
computationalquantumchemistry,calculationsfordescribingmoleculesareaccom-
plished by first clamping the nuclei at fixed positions, and this strategy leads to
results that lack the symmetries of the full-quantum problem; on this basis, they
conclude that, at present, molecules’ nuclear structure still needs to be put in by
hand.Thepurposeofthethirdchapterofthispart,“AbouttheNatureoftheWave
Function and its Dimensionality: The case of Quantum Chemistry,” by Sebastian
FortinandJesúsA.JaimesArriaga,istofacetheproblemposedbythefactthatthe
quantumwavefunctionisdefinedonaspaceof3Ndimensions(withNthenumberof
particles),whereasthedescriptionsinquantumchemistryareframedinthephysical
3-dimensional space. By focusing on the so-called “independent electron approxi-
mation,” the authors claim that the concept of orbital is not a mere approximation
thatcouldberemovediftheexactsolutionwereaccessible,butitplaysanessential
roleinquantumchemicalexplanations.Finally,inthechapter“CoarseGrainingand
the Quantum Theory of Atoms in Molecules,” which closes the third part and the
volume, Olimpia Lombardi and Chérif F. Matta address the nature of the electron
densityinthecontextoftheQuantumTheoryofAtomsinMolecules(QTAIM).By
showing that the electron density is a coarse-grained magnitude when considered
fromtheviewpointofquantummechanics,theauthorsclaimthatthewayinwhich
