This work has been supported by Peru's Consejo Nacional de Ciencia y Tecnologia (CienciActiva - CONCYTEC) and the British Embassy in Lima [contract numbers 154-2015 and 002-2016]. Portions of this research were conducted with the advanced computing resources provided by Texas A&M High Performance Research Computing. Ms. Karinna Visurraga (UTEC) is kindly acknowledged for administrative support.

Cyanidation (leaching with cyanide) is a common yet complex surface process in hydrometallurgical practice, and its effectiveness in extracting the metal of interest is often affected by the nature of the mineralogical species that are present. Little is known about surface processes on acanthite (a silver sulfide) and how its various facets respond to cyanidation in aqueous solution. Therefore, in this work, some properties of both bulk acanthite (Ag2S) and its (001), (022), and (1̅21) surface facets have been studied by density-functional-theory (DFT)-based calculations to elucidate reactivity trends and competitive adsorption (initial stages in the surface process of cyanidation) between cyanide and other species present in the leaching liquor. It is found that CN– binds by its C-end to silver sites on the acanthite surface with adsorption energy similar to that of OH– but strong...