Structural phase stability and superconductivity of LaN

Results of a theoretical investigation on the structural phase stability of lanthanum nitride (LaN) is reported. We predict that LaN, which crystallizes in NaCl structure, undergoes a transition from NaCl to CsCl type structure at around 26.9 GPa with a volume collapse of 12.5%. In addition, the superconducting transition temperature (T-c) is also calculated theoretically for the first time. The high-pressure phase of LaN is CsCl structure and not the tetragonal structure as observed in other lanthanum pnictides, which has been predicted by the total energy minimization. In addition, the basic ground state properties such as the equilibrium lattice parameter, bulk modulus, cohesive energy, heat of formation, electronic specific heat coefficient are computed and compared with the available experimental and other theoretical results. The band structure and density of states are plotted for ambient and high-pressure structures. The possible reasons for the occurrence of superconductivity and the structural phase transition are also discussed. (C) 2002 Elsevier Science Ltd. All rights reserved.