Bohm's Quantum Theory of Motion for quantum chemistry

SEBASTIAN FORTIN; JUAN CAMILO MARTÍNEZ GONZÁLEZ; OLIMPIA LOMBARDI

Boca Raton

Congreso; 2016 ISPC International Society for Philosophy of Science Annual Symposium; 2016

International Society for the Philosophy of Chemistry (ISPC), Florida Atlantic University

The relationship between chemistry and physics has been one of the most important topics in the recent philosophy of chemistry. In this context, the links between theories coming from both disciplines have been explored with great detail from different perspectives. However, despite this effort, there is still no agreement between specialists with respect to which is the best intertheoretic relationship for describing the links between chemistry and physics.According to the orthodox view, it is possible to reduce chemistry to quantum mechanics: the difficulties are only due to the complexity of the equations. For this reason, in practice physicists introduce some approximations to simplify calculations. However, in some cases approximate methods can deform the heart of quantum mechanics, in such a way that the reduction?s success is disputed (Woolley 1976, 1978, 1998). Some authors claim that approximations introduce assumptions that are incompatible with quantum mechanics itself (Lombardi and Castagnino 2010, Chang 2015). On the other hand, the description of certain basic elements for chemistry in quantum terms has proven to be problematic. For instance, the concept of molecular structure finds no place in the theoretical framework of quantum mechanics because it appeals to a classical notion as fixed nuclei positions (Woolley 1978). The nature of chemical bond and orbitals seems to be alien to the quantum mechanics perspective (Vemulapalli 2008, Labarca and Lombardi 2010, Llored 2010, Hendry 2012).Most of the philosophical difficulties mentioned above are consequences of the peculiar features of ordinary quantum mechanics. However there is an alternative quantum formalism proposed by David Bohm in 1952. The Quantum Theory of Motion (Holland 1993) writes the Schrödinger equation in a different but equivalent way. The result is an equation that is formally identical to the Hamilton-Jacobi equation of classical mechanics, where a classical potential is added to the quantum terms. This novel term is then interpreted as a quantum contribution to the total potential. On the basis of this fact, the Quantum Theory of Motion proposes a new quantum theory in which the classical equations and the classical ontology are maintained, but a new fundamental force is introduced, the quantum force. Thus one obtains a deterministic quantum mechanics in which particles have definite positions and velocities at any given time, i.e. they have well-definite paths.In this work we propose a perspective different from the traditional one to analyse philosophical problems in quantum chemistry. We claim that the introduction of the Quantum Theory of Motion may clarify some problems and to dissolve others. The possibility of definite positions for fixed nuclei simplifies the interpretation of the approximations in quantum chemistry. On the other hand this theory allows us to analyse the position of an electron in a chemical bond. In the particular case of the simple H-H covalent bond, computations lead to conclude that the electrons are in the middle of the two nuclei. In this way, we recover the ?picture? of the classical chemistry viewpoint.As a conclusion, we propose to explore the possibility that, from the conceptual point of view, the Quantum Theory of Motion be a more adequate theory for quantum chemistry.