Finite Size Effect in Path Integral Monte Carlo Simulations of 4 He Systems

Path integral Monte Carlo (PIMC) simulations are a powerful computational method to study interacting quantum systems at finite temperatures. In this work, PIMC has been applied to study the finite size effect of the simulated systems of 4 He. We determine the energy as a function of temperature at saturated-vapor-pressure (SVP) conditions in the temperature range of T ε [1.0 K,4.0 K], and the equation of state (EOS) in the ground state for systems consisted of 32, 64 and 128 4 He atoms, respectively. We find that the energy at SVP is influenced significantly by the size of the simulated system in the temperature range of T ε [2.1 K, 3.0 K] and the larger the system is, the better results are obtained in comparison with the experimental values; while the EOS appeared to be unrelated to it