Theoretical Study On Vacuum Thermal Decomposition Of Arsenic Iron Slag

By calculating the Gibbs free energy of thermal decomposition reactions of iron-arsenic and tin-arsenic compounds under vacuum situation, we got the reactions may occur under1463K,30Pa. The plane-wave pseudopotential method based on density functional theory have been carried out to calculate the stable structure of FeAs, FeAs2, Fe2As, Sn4As3and SnAs. Then ab initio molecular dynamics method have been used to study the thermal decomposition process under1463K,30Pa and1373K,30Pa respectively. The stabile structural of AS2-AS4molecules were obtained by B3LYP hybrid functional method, and then the QST (quadratic synchronous transit) method have been used to search the transition state between gaseous arsenic molecules. The results show that:Under simulated conditions, the removal of arsenic depend on the collision of the As atoms in the supercell. Arsenic may be removed stepwise under the simulated situation, and is likely to be separated out in the form of As2. Under simulated conditions of1463K and1373K, temperature has a great influence on the As-Fe bonds decomposition in FeAs and FeAs2supercell. While the influence on Sn-As bond decomposition in Sn4As3and SnAs is not so significant. Volatilization of Sn atoms in SnAs and Sn4As3supercell may occur while at high temperatures. And At the interface, Sn4As3(100) surface and SnAs (100) surface structure has a phenomenon that two As2molecular generate to be a structure of AS4, and the Sn atoms also have a tendency to generate to complex clusters.