First-Principles Calculations For Physics Properties Of Pu,NaCl And SrO

Since superconductivity was first discovered in Mercuy by Onnes in 1911,superconductivity has become one of the most interesting areas. Recently, propertiesof material at high pressures and high temperatures have been the objects of intensiveexperimental and theoretical investigations.Firstly, two structure of Pu is investigated by ab initio field theory, using thelocal density approximation and the Troullier-Martins type of pseudopotential, and thelattice constant a, the bulk modulus B₀, the first order pressure derivative of bulkmodulus B'₀, the superconducting transition temperature and the elastic constants are obtained.Secondly, the transition phase of NaCl from the B1 to the B2 structures is alsoinvestigated. It is found that the transition from the B1 structure to the B2 structureoccurs at the pressure of 28.3 GPa, as is well consistent with the experimental dataand other theoretical results. The heat capacity of the B1 and the B2 structures ofNaCl are obtained for several pressures. It is shown that when T＜1500 K, the heatcapacity C_V is dependent on both the temperature T and the pressure P. However, athigher pressures and/or higher temperatures, the anharmonic effect on C_V issuppressed, and C_V is very close to the Dulong-Petit limit. The heat capacity C_V in thiswork is 33.97 J mol^-1 K^-1 at zero pressure and ambient temperature, well consistentwith the experimental data and other theoretical results.Finally, using the same methods above, the transition phase of SrO from the B1to the B2 structures is also investigated. The heat capacity of the B1 and the B2structures of SrO are obtained for several pressures. It is shown that when T＜1200 K, the heat capacity C_V is dependent on both the temperature T and the pressure P.However, at higher pressures and/or higher temperatures, the anharmonic effect on C_Vis suppressed, and C_V is very close to the Dulong-Petit limit. The heat capacity C_V inthis work is 27.10 J mol^-1 K^-1 at zero pressure and ambient temperature, wellconsistent with the experimental data and other theoretical results.