Estimation of bulk moduli of compounds by empirical relations between bulkmodulus and interatomic distance

Relations between bulk modulus and interatomic distance were empirically de termined for five groups of elemental substances by using power functional forms, B = Cd-m, where In and C are the constants. The power value for sp(3 )-bonded elemental substances was determined to be -3.60 and the value is q uite close to the one (= -3.5) reported previously. It is indicated that bu lk moduli of various AB compounds can be estimated using the respective mod ified power functional formula based on the formulas for the five groups of elemental substances, by assuming that power and preterm can be determined by geometrical mean of these values of the basic power functional formulae for the constituent elements. Excellent agreement with experimental bulk m oduli was obtained for tetrahedrally coordinated (sp(3)-bonded) AB compound s with B3 and B4 crystal structures. For AB type carbides, nitrides and oxi des with B1 and B4 crystal structures and for several rare-earth oxides, th e estimated bulk moduli show a good agreement with experimental ones except several compounds. It is also suggested that these power functional formul ae can be available for predicting new hard materials. (C) 2000 Elsevier Sc ience B.V. All rights reserved.