Interactions of nerve agents with model surfaces: Computational approach

The development of cost effective, cleanup technologies for organophosphorus contaminants continue to be a high priority for environmental restoration research. Such development involves the coordination of experimental and theoretical investigations to understand and integrate both technological and fundamental aspects of key processes. Although the major processes affecting the natural and engineered treatment of organophosphates have been appreciated qualitatively, many questions remain regarding their reaction mechanisms. Unique properties of clay minerals and metal oxides such as high adsorption and catalytic ability have resulted in their applications as natural adsorbents and catalysts in the development of cleanup technologies. An understanding of the physical and chemical characteristics of the contaminants, adsorption sites of selected catalytic materials, details of sorption of contaminants on soil, on soil in water solution, and also their distribution within the environment is of particular interest. Application of computational chemistry can provide deeper insight into the aforementioned characteristics of organophosphorus compounds as is discussed in this article. Theoretical models were developed that explain and predict how clay minerals and metal oxides, their type and size, and adsorption site can affect the adsorption and decomposition of selected nerve agents and their simulants, and the influence on many factors including the presence of cations, water, and different used computational methods and techniques was analyzed. Several different initial positions and orientations of organophosphate molecules on models of metal oxides and clays were tested. The results show that the small fragments of metal oxides and clay minerals are much more reactive toward the adsorption of organophosphates which under certain conditions can lead to their decomposition. On the other hand, decrease in ionicity of metal oxides results in lowering of the binding affinity toward such compounds. (C) 2010 American Vacuum Society [DOI: 10.1116/1.3271148]