A SCRF-CNDO/2 study on proton conductivity mechanisms in hydronium perchlorate. Towards a quantum chemical representation of defects and impurities in crystals

Abstract

A quantum chemical scheme adapted to study charge separation processes in crystalline molecular/ionic defects is presented. The scheme derives from a generalized self-consistent reaction field theory of surrounding medium effects. Computational implementation has been done at the CNDO/2-INDO approximate level; lattice sums are performed by direct summation techniques. The sums are essential for building the static dielectric response function of the crystal to the field set up by the defect charge density and the Madelung potential created by the surrounding crystal permanent charge density. The scheme has been applied to study some aspects of the proton conductivity mechanism in crystalline hydronium perchlorate. The theoretical results lend support to an experimentally grounded molecular mechanism. The theoretical scheme can easily be extended to describing chemical processes taking place at crystal surfaces.