Molecular thermodynamics of quantum square-well fluids using a path-integral perturbation theory

作者：Serna Cesar; Gil Villegas Alejandro^*

来源：Molecular Physics, 2016, 114(18): 2700-2716.

DOI：10.1080/00268976.2016.1173732

• Perturbation theory
• quantum fluids
• path-integral Monte Carlo
• semiclassical methods

We present a thermodynamic perturbation theory for fluids composed of N quantum particles of diameter and mass m contained within a volume V at temperature T, interacting via a pair square-well potential (SW) with energy depth epsilon and range . Our approach is based on the exact analogy between the discretised path- integral formalism of quantum mechanics and the partition function of a classical system composed of necklace molecules, introducing a Zwanzig expansion method, using a quantum hard-spheres fluid (QHS) as reference system in order to calculate the perturbation terms for the Helmholtz free energy A(QSW) of the SW system. These terms are obtained with path-integral Monte Carlo simulations in the canonical ensemble, and analytical results are provided as functions of the inverse temperature = 1/kT, density (*) = N sigma(3)/V, SW range and de Broglie thermal wavelength , where h and k are the Planck's and Boltzmann's constants, respectively. Accurate results are obtained for thermodynamic states comprised in the region (*) 0.7, 1.2 1.8, and *(B) 0.9. Quantum effects are more noticeable for shorter SW ranges, although the main thermodynamic effects are given by the QHS free energy.

• 出版日期2016-9