Bond Length, Cohesive Energy, and the Bulk Modulus

7-B Bond Length, Cohesive Energy, and the Bulk Modulus 

We may predict the bond length in a solid by minimizing the total energy, or maximizing the of Eq. (7-3), with respect to d. Thus, to the energy per atom labelled overlap in I ig. 7-1, from Hqs. (7-1) and (7-2) we add p , which docs not depend upon d, and —, which varies asd, at least near the equilibrium 

A consideration of Fig. 7-1 indicates that the discrepancies must arise from an error in the overlap interaction in which the kinetic term and the term from Coulomb and exchange interaetions almost exactly cancel at the ob,served spacing. No minor modification of the bond energy could bring the minimum to the observed position, and a major modification would disrupt the agreement with 

We may proceed to two other predictions that can be made on the basis of Fig. 7-1, the cohesive energy (the value of E o, at the minimum) and the bulk modulus (proportional to the curvature, at the minimum). The re- 

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