Helmholtz free-energy high-temperature perturbation expansion for square-well and square-shoulder potentials

Sastre, Francisco; Sotelo-Serna, Maria Guadalupe; Moreno-Hilario, Elizabeth; Benavides, Ana Laura

doi:10.1080/00268976.2021.1887527

Cited by 8 publications

(2 citation statements)

References 63 publications

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“…22,21 Higher-order perturbation coefficients are very difficult to infer from simulation, 23 but the perturbation ratios show trends that are "unsurprising" if not yet entirely predictable. 22,24 Knowing the intercepts of these ratios can be very valuable in this context. A related incidental result is the orientationally averaged Mayer function for the reference term used to compute B 20 .…”

Section: ■ Incidental Implicationsmentioning

confidence: 99%

“…Although perturbation coefficients approach zero at zero density, the ratios of perturbation coefficients approach finite values. The zero-density intercepts of those ratios are given by the ratios of the pertinent perturbative second virial coefficients. , Higher-order perturbation coefficients are very difficult to infer from simulation, but the perturbation ratios show trends that are “unsurprising” if not yet entirely predictable. , Knowing the intercepts of these ratios can be very valuable in this context.…”

Section: Incidental Implicationsmentioning

confidence: 99%

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On-the-Fly Second Virial Coefficients

Elliott

2021

J. Phys. Chem. B

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A simple but approximate algorithm is described for computing second virial coefficients based on equilibrated molecular configurations that may be generated during any Monte Carlo or molecular dynamics simulation. The algorithm uses simple quadrature based on sampling every binary pair in the configuration and moving their center–center distances from zero to infinity. Comparisons are made in the literature results using more sophisticated sampling and integration for n-alkanes of ethane through n-dodecane. Accuracy is within the error bars determined by block averaging, and temperature effects can be inferred using a single configurational temperature, including perturbative virial coefficients. Predictably, the accuracy is best at the configurational temperature and when the configurational density is lowest. More notably, good accuracy is achieved from configurations at intermediate densities, and the trend at high density conveys valuable insight about conformational changes. The algorithm is simple enough to assign as a homework problem in an introductory molecular modeling course and reinforces the elementary knowledge of pairwise potentials among multisite molecules, numerical integration, and conformational averaging. The result is also quite valuable on its own merits, especially considering thermodynamic integration to compute phase equilibria. Additionally, the incidental data derived from the computation can provide simple but meaningful insights into the nature of multisite interactions, as demonstrated by relating the Mayer averaged potential to an effective Mie potential. Altogether, the argument is made that the computation of the second virial coefficient should be considered to be a routine metric of any molecular simulation, such as the radial distribution function, pressure, or energy.

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Section: ■ Incidental Implicationsmentioning

confidence: 99%