Thermodynamic properties and heat capacity of Ru metal in HCP, FCC, BCC and liquid state

Abstract

Isometric heat capacity c v and isobar heat capacity c p of Ru metal in HCP, FCC, BCC and liquid state were calculated by using pure element systematic theory. The results are in good agreement with joint army-navy-air force (JANAF) experimental value and the calculation result by first-principle (FP) method. But the results have great differences in contrast to Scientific Group Thermodata Europe (SGTE) database. The cause is found that it cannot neglect the electron devotion to heat capacity to adjust c p in one-atom (OA) method. The disparity between OA method and SGTE database was discussed. The main cause is that OA method adopts the crosspoint with iso- E c -line and iso- a-line in hybritriangle to determine the properties, but SGTE database is obtained by extrapolation from activity measurements and critical assessment of data from a large number of binary system. Thermodynamic properties of Ru metal in HCP, FCC, BCC and liquid state, such as entropy S, enthalpy H and Gibbs energy G were calculated. Therefore, the full description of thermodynamic properties from 0 K to random temperature is implemented.