A local topological view of pressure-induced polymorphs in SiO2

作者：Morales Garcia A^*; Marques M; Menendez J M; Franco R; Baonza V G; Recio J M

来源：Theoretical Chemistry Accounts, 2014, 133(12): 151-158.

DOI：10.1007/s00214-014-1578-2

• DFT calculations
• High pressure
• QTAIM
• Silica

By means of the quantum theory of atoms in molecules (QTAIM), we carry out a microscopic analysis of the response to hydrostatic pressure (p) of alpha-quartz, coesite, stishovite, CaCl2-type, and alpha-PbO2-type polymorphs of silica (SiO2). According to QTAIM atomic charges, there is not a substantial change in the ionic character of the bonding network (often described as polar covalent) along the pressure-induced polymorphic sequence. Atomic volumes (V-i) reveal that Si atoms remain with similar values regardless the polymorph, whereas oxygen follows the same volume collapses as the unit cells upon phase transformations. The inert character of Si is also displayed when local pressures (p(i) = -dE/dV(i), E is the energy per formula unit) are computed. We obtain linear trends (p(Si) = 9.40 p and pO = 2.22 p) with a greater slope in the case of Si, illustrating its greater resistance to reduce its volume as pressure is applied. QTAIM also allows the evaluation of the atomic contributions to the bulk compressibility. Interestingly enough, we found a change in the atom showing the lowest compressibility, which is silicon in low-pressure phases but oxygen for stishovite and post-stishovite polymorphs.

• 出版日期2014-10-24