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

Relations between bulk modulus and interatomic distance were empirically determined 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 quite close to the one (= -3.5) reported previously. It is indicated that bulk moduli of various AB compounds can be estimated using the respective modified 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 moduli was obtained for tetrahedrally coordinated (sp(3)-bonded) AB compounds with B3 and B4 crystal structures. For AB type carbides, nitrides and oxides with B1 and B4 crystal structures and for several rare-earth oxides, the estimated bulk moduli show a good agreement with experimental ones except several compounds. It is also suggested that these power functional formulae can be available for predicting new hard materials. (C) 2000 Elsevier Science B.V. All rights reserved.