ИСТИНА

We apply previously developed Deductive Molecular Mechanics1 based on (i) representing the molecular electronic structure through antisymmetrized products of the group functions of the observable parts of the molecule - generalized chromophores, and (ii) determining the form and orientation of the hybrid orbitals spanning the carrier subspaces for these chromophores from the minimum condition for the total energy. This approach have been implemented by us in the SLG method,2 which allowed us to reduce the dependence of the computational costs on the molecule size down to O(N). The suggested combination of the assumptions yields not only numerical efficiency, but also permits to prove statements (theorems) concerning electronic structure either general or related to concrete molecules. Very recently we have proven the nonexistence of the “banana” bonds in the C2 molecule and formulated the conditions when this particle can exist as an aggregate of either two divalent or two tetravalent carbon atoms.3 In the present work we apply a similar approach to studying the origin of the phase diagram of ices. We start from establishing the energy expression for highly symmetric form of non-molecular ice (ice X) as for a system of oxygen atoms connected by hydrogen bonds and prove mathematically the stability of this polymorph under external pressure above critical. For pressures below critical we derive the expressions describing the pressure dependence of the interaction energy of the effective dipoles emerging in the system when the symmetric lay-out of the hydrogen atoms among the oxygen atoms, characteristic for ice X, breaks down. This dependence allows us to reproduce qualitatively and understand the characteristic and unusual (as compared to the others) form of the boundary between the existence areas of the ordered and disordered ices VIII and VII. We also discuss the possibility of describing the differences between the ices existing at lower pressures (down to normal) on account of terms dependent on global structure including the long-range electrostatic contributions. This work is supported in the frame of initiative of joint trilateral German-Russian-Ukrainian research in the area of Natural Science by the Volkswagenstieftung.