Interrelations between EOS parameters and cohesive energy of transition metals: Thermostatistical approach, ab initio calculations and analysis of "universality" features

D. BERTOLDI; S. B. RAMOS; A. FERNÁNDEZ GUILLERMET

JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS

PERGAMON-ELSEVIER SCIENCE LTD

Lugar: Amsterdam; Año: 2017 vol. 107 p. 93 - 99

0022-3697

We present a theoretical analysis of the equation of state (EOS) of metals using a quasiharmonic Einstein model with a dimensionless cohesive energy versus distance function (F(z)) involving the Wigner-Seitz radius and a material-dependent scaling length, as suggested in classical works by Rose, Ferrante, Smith and collaborators. Using this model, and "universal" values for the function and its first and second derivatives at the equilibrium distance (z = 0), three general interrelations between EOS parameters and the cohesive energy are obtained. The first correlation involves the bulk modulus, and the second, the thermal expansion coecient. In order to test these results an extensive database is developed, which involves available experimental data, and results of current ab initiodensity-functional-theory calculations using the VASP code. In particular, the 0 K valuesfor volume, bulk modulus, its pressure derivative, and the cohesive energy of 27 elementsbelonging to the first (Sc, Ti, V, Cr, Fe, Co, Ni, Cu, Zn), second (Y, Zr, Nb, Mo, Tc, Ru,Rh, Pd, Ag, Cd) and third (Hf, Ta, W, Re, Os, Ir, Pt, Au) transition row of the PeriodicTable are calculated ab initio and used to test the present results. The third correlationobtained, allows an evaluation of the third derivative of F(z) at z = 0 for the current elements.With this new information, a discussion is presented of the possibility of finding a"universal" F(z) versus z function able to account accurately for the pressure derivative ofthe bulk modulus of the transition elements.