Factorization of 3-Point Static Structure Functions in 3D Yukawa Liquids

Magyar, Péter and Hartmann, P. and Kalman, Gabor J. and Golden, Kenneth I. and Donkó, Zoltán (2016) Factorization of 3-Point Static Structure Functions in 3D Yukawa Liquids. Contributions to Plasma Physics, 56 (9). pp. 816-829. ISSN 0863-1042

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Abstract

In many-body systems the convolution approximation states that the 3-point static structure function, S (3) (k1 , k2 ), can approximately be “factorized” in terms of the 2-point counterpart, S (2) (k1 ). We investi- gate the validity of this approximation in 3-dimensional strongly-coupled Yukawa liquids: the factorization is tested for specific arrangements of the wave vectors k1 and k2, with molecular dynamics simulations. With the increase of the coupling parameter we find a breakdown of factorization, of which a notable example is the appearance of negative values of S(3)(k1,k2), whereas the approximate factorized form is restricted to positive values. These negative values – based on the quadratic Fluctuation-Dissipation Theorem – imply that the quadratic part of the density response of the system changes sign with wave number. Our simulations that incorporate an external potential energy perturbation clearly confirm this behavior.

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