Ab initio methods in mineral surface reactions

Abstract

The methodology of nonempirical ab initio quantum mechanical calculations is reviewed as applied to the field of mineral surface chemistry and water‐rock geochemical kinetics. The ab initio treatment of adsorption deals with the covalent forces between surface atoms and molecules either in solution or in the gas phase. This new information on the bonding of surface atoms can now extend the classical theory of adsorption. Furthermore, reactions on mineral surfaces can also be understood with the aid of ab initio results. The theory can predict reaction potential surfaces as a function of the position of various surface species. In turn, such entities as the activated complex of transition state theory and the reaction coordinate can now be described in a nonempirical way for geochemical reactions, such as the dissolution of quartz or feldspar. Other important reaction variables such as the kinetic isotope effects, the catalytic effect of pH, the catalytic or inhibitory role of dissolved ions and of organic molecules, and the effect of impurities and coordination number of the surface atoms on the water‐rock kinetics can be uniquely studied with ab initio techniques. The initial success of the ab initio approach opens up a new and powerful method of investigating surface reactions.