Reclaiming the "identity" of atoms in molecules and crystals as "real-space" quantum subsystems
Since the discovery of electron, at the dawn of the previous century, atoms gradually lost their position as "fundamental" building block of matter and instead matter is conceived to be composed electrons and nuclei as far as one is not concerned with the high-energy physics. In contrast to this "paradigm" shift in theoretical physics, most experimental scientists in condensed matter physics, chemistry, material science and molecular biology are yet conceiving matter in various forms, e.g. molecules, biomolecules, crystals, as composed of atoms and ions as the basic "subsystems". However, quantum mechanics, as the standard language of theoretical physics in these domains, has no "intrinsic" recipe how a "real-space" subsystem must be defined. And, here comes the tension: How atoms/ions in molecules/crystals may claim their identity from a theoretical viewpoint? In this talk I will consider this issue using a theoretical framework known as the Quantum Theory of Atoms In Molecules (QTAIM), which is the "natural" framework to define and characterize the AIM in real-space. It will be demonstrated that this theory is capable of introducing both "morphology" and "property" to the AIM using the wavefunction or the density matrix of the system, i.e. a molecule or a crystal. Next, the newly extended QTAIM, termed the multi-component QTAIM (MC-QTAIM), will be introduced and it will be demonstrated that this new theory widens the concept of AIM much beyond the traditionally known domains, e.g. exotic molecular species. Also, it will be shown that MC-QTAIM is a natural framework to answer some fundamental questions about the very nature of AIM. Eventually, some speculations will be done on the future of this field of research with possible applications in molecular and condensed matter physics.
Dr. Shant Shahbazian
6 September 2017
Farmaniyeh Building, Conference Hall