A first-principles DFT study of UN bulk and (001) surface: Comparative LCAO and PW calculations

摘要: LCAO and PW DFT calculations of the lattice constant, bulk modulus, cohesive energy, charge distribu- tion, band structure, DOS for UN single crystal are analyzed. It is demonstrated that a choice uranium atom relativistic effective core potentials considerably affects structure magnetic at low tem- peratures. All indicate mixed metallic-covalent chemical bonding in with U5f states near Fermi level. On basis experience accumulated simulations, we compare atomic elec- tronic as well formation energy UN(001) surface calculated on slabs different thickness using both approaches. thermal conductivity, melting temperature, metal density when compared dioxide commonly used nowadays. To predict nuclear fuel performance under operating con- ditions then prolonged time repository fuel, it necessary to understand material physicochemical properties. Of special importance properties because commercial fuels powders UN, UC effectively oxidized air. The more so, numerous grain boundaries consider- ably affect Theoretical studies compounds difficult due character electron motion U strong electron-electron correlation. Moreover, rather complicated system characterized by metal-covalent bonding. metallic part (U5f level) better described delocalized Plane Waves (PW), whereas covalent (U5f-N2p hybridization) Linear Combination Atomic Orbital (LCAO) set. This why this article results In Section ''Previous ab initio simulations bulk,'' comparison made (studied earlier experimentally), detailed analysis pseudopo- tentials ''Current bulk.'' ''DFT surface'' section, discuss—for first time—the (001) sur- face (so far, atomistic compound substrates were performed only densely packed UO2 surfaces 2 ).