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From Quantum Physics to Quantum Chemistry: Study of a Transformation and Its Consequences against Intertheoretic Reduction

The first part of the talk, which is mainly anthropological, summarizes the results of a survey that we carried out in several research laboratories in 2010. Our aims were to understand what quantum chemists currently do, what kind of questions they ask, and what kind of problems they have to face when creating new theoretical tools for understanding chemical reactivity and predicting chemical transformations.The second part, which is mainly historical, highlights the philosophical underpinnings that structure the development of quantum chemistry from 1920 to nowadays. In so doing, we will discuss chemical modeling in quantum chemistry, and the different strategies used in order to define molecular features using atomic ones and the molecular surroundings at the same time. We will show how computers and new laboratories emerged simultaneously, and reshaped the culture of quantum chemistry. This part goes on to describe how the debate between ab initio and semi-empirical methods turned out to be highly controversial because of underlying scientific and metaphysical assumptions about, for instance, the nature of the relationships between science and the possibility for human knowledge to reach a complete description of the world.

The third and last part is about the philosophical implications for the study of quantum chemistry and that of ‘quantum sciences’ at large. It insists on the fact that the history of quantum chemistry is also a history of the attempts of chemists to establish the autonomy of their theories and methods with respect to physical, mathematical, and biological theories. According to this line of argument, chemists gradually proposed new concepts in order to circumvent the impossibility to perform full analytical calculations and to make the language of classical structural chemistry and that of quantum chemistry compatible. Among different topics, we will query the meaning of a chemical bond, the impossibility to deduce a molecular shape from the Schrödinger equation, the way quantum chemistry is involved in order to explain the periodic table, and the possibility to go beyond the Born-Oppenheimer approximation. We would like to show that quantum chemistry is neither physics nor chemistry nor applied mathematics, and that philosophical debates which turned out to be relevant in quantum physics are not necessarily so in quantum chemistry, whereas other philosophical questions arise, which, clearly question the relevance of intertheoretic reduction to study and understand science.

Author Information:

Jean-Pierre Llored

Laboratory SPHERE, University Paris 7, France / Linacre College, Oxford, UK