Theoretical Study of the Adsorption of Organophosphorous Compounds to Models of a Silica Surface

Abstract

We present a study of the interaction of seven organophosphorous (OP) compounds with models of a silica surface using electronic structure calculations. Two of the OP species are chemical-warfare nerve agents (sarin and soman) and the rest are organophosphate (methyl dichlorophosphate, dimethyl chlorophosphate, and trimethyl phosphate) or organophosphonate (dimethyl methylphosphonate and diisopropyl methylphosphonate) mimics utilized in recent experiments. Calculations that approximate an amorphous silica surface by a simple gas-phase silanol molecule qualitatively reproduce the trend in binding energies determined in recent ultrahigh vacuum experiments. These calculations also show that, of the various atoms in the OP species that can accept hydrogen bonds from silanol groups, the oxygen atom that forms a double bond with the central phosphorus atom provides the largest binding energy, followed first by the remaining oxygen atoms and then by the halogen atoms. Quantitative comparisons with experiments ar...