The Irving-Kirkwood procedure can be used to find a macroscopic stress tensor that depends on both momentum density and this quantity. For 10 points each:
[10e] Name this quantity that for a liquid is approximately equal to its kinetic energy. Weeks, Chandler, and Anderson name a commonly used modification of one example of this quantity named for Lennard-Jones.
ANSWER: potential energy [accept Lennard-Jones potential or LJ potential or WCA potential]
[10h] The Ornstein-Zernike equation can be used with a closure relation like the Percus-Yevick approximation to compute this function for a liquid. The Mayer cluster expansion uses this function that is proportional to “e to the minus beta U” at long distances.
ANSWER: radial distribution function [or pair correlation function; accept RDF; prompt on g of r]
[10m] The Percus-Yevick equation has an analytical solution for this model of liquids. In this model, the pairwise potential is infinite below a certain radius and zero above it, meaning that particles “exclude volume.”
ANSWER: hard sphere model [accept hard disc model]
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