Force Fields in Liquid and Solid Cu Metal: Relation Between Quantum Chemical and Density Functional Treatments

Abstract

Two lypes of force field are compared and contrasted for condensed Cu in metallic phases. The first is a conventional liquid metal pair potential, accessible through inversion of the measured liquid structure factor S(q). The form of this, for T=1423 K, and number density ρ=0.075 54 ų is known from the very recent work of Rajagopalan and Srinivasa Rao and from the earlier study of Arai and Yokoyama. This potential is suitable to discuss structural rearrangements only at the specific atom volume Ω=ρ¹ referred to above.

The second type of force field is appropriate for crystalline Cu lattices with different local coordination numbers. As a concrete example, the work of Carlsson et at. on face-centered-cubic Cu metal is analyzed in terms of the ¹Σ_g and ³Σ_u potential energy curves of the free-space Cu dimer. The relation to Cu clusters is briefly referred to.

Key Words:

• Local coordination numbers
• structure factor inversion
• copper dimer