Article,

Split series potential energy function

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Journal of Mathematical Chemistry, 49 (6): 1180-1191 (June 2011)10.1007/s10910-011-9806-7.

Abstract

A split series potential energy function is developed herein such that it can be primarily reduced into generalized forms of Lennard-Jones, Morse, Buckingham, Linnett, and anything in between them by altering the type-parameters. Unlike the previous approach whereby the type-parameters act as weighting parameter between the inverse power and the exponential decay terms, the current approach attaches the type-parameters as indices to the denominator of every summation term. A change of the index shifts the series summation to mimic a curve that is representative of an inverse power, an exponential index, or a weighted proportion between the two. Comparison with the Lennard-Jones (12–6) and Exponential-6 (both ξ = 13.772 and ξ = 12) in the case of uncharged non-bonded interactions by using type-parameters (p, q) = (0, 0) and (p, q) = (1, 0) respectively in the model gives very good correlation. Comparison with the Morse potential in the case of bonded interaction by using (p, q) = (1, 1) gives excellent agreement. All results show that the use of only five expansion terms is sufficient for providing good agreement with the classical potentials. Better fit to experimental data and ab initio results are expected with the incorporation of coefficients in every term of the series expansion. The proposed model is useful for modeling the transition state from solid to fluid and vice versa.

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