Energy, compressibility, and covalence in the group carbon family

It is shown that a similarity relationship of the type (K0V0/E-0) congruent to const (where K-0, V-0, and E-0 are the bulk modulus, the volume, and the total energy at P = 0) exists for the elements of the carbon family, including C, Si, Ge, Sn, and Pb. This fact rules out the possibility of significant covalent effects on the compressibility of the corresponding substances. The record bulk modulus value of diamond is associated with its extreme atomic density. (C) 2000 MAIK Nauka/Interperiodica.