Hidden aspects of the Structural Theory of chemistry: The MC-QTAIM analysis reveals 'alchemical' transformation from a triatomic to a diatomic structure

摘要

The Structural theory of chemistry introduces chemical/molecular structure asa combination of relative arrangement and bonding patterns of atoms inmolecule. Nowadays, the structure of atoms in molecules is derived from thetopological analysis of the quantum theory of atoms in molecules (QTAIM). Inthis context a molecular structure is varied by large geometrical variationsand concomitant reorganization of electronic structure that are usually takingplace in chemical reactions or under extreme hydrostatic pressure. In thisreport a new mode of structural variation is introduced within the context ofthe newly proposed multi-component QTAIM (MC-QTAIM) that originates from massvariation of nuclei. Accordingly, XCN and CNX series of species are introducedwhere X stands for a quantum particle with a unit of positive charge and avariable mass that is varied in discrete steps between the masses of proton andpositron. Ab initio non-Born-Oppenheimer (non-BO) calculations are done on bothseries of species and the resulting non-BO wavefunctions are used for theMC-QTAIM analysis revealing a triatomic structure for the proton mass and adiatomic structure for the positron mass. In both series of species a criticalmass between that of proton and positron mass is discovered where thetransition from triatomic to diatomic structure takes place. This abruptstructural transformation has a topological nature resembling the usual phasetransitions in thermodynamics. The discovered mass induced structuraltransformation is a hidden aspect of the Structural theory which is revealedonly beyond the BO paradigm when nuclei are treated as quantum waves instead ofclamped point charges.