The Use of the Coordination Number in the Interpretation of Fluid Structure

Abstract

Use of radial distribution data, g(r), to compute a coordination number, N ₁, for liquids is discussed for four methods: A, symmetrizing the first peak in rg(r); B, symmetrizing the first peak in r²g(r); C, decomposition of r²g(r) into shells; and D, computation of area to the first minimum in r²g(r). Experimental liquid structure data for argon at 13 states were used to compute N₁ for each of the four methods. Theoretical computations were also made at low densities employing a cluster integral expansion of g(r). N ₁ is a strong function of density, varying for method B from N ₁ = 0 at ∊ = 0 to N ₁= 6 for ∊ 2 ∊ at temperatures near T _c. At ∊ 2 ∊ values for N ₁ for methods A, B, C, and D are 5.3, 6.0, 6.6, and 7.5.