TITLE:
Comparative Classical and Quantum Molecular Dynamics of Dense-Phase of Noble Gases at Low Temperatures
AUTHORS:
Kanabet Yapara, Abdallah Brahim Elhadj Ali, Pale Wang-Yang, Foulla Dieudonne Platou, Steve-Jonathan Koyambo-Konzapa
KEYWORDS:
Quantum Effects, Zero-Point Energy, Molecular Dynamics, Path Integral Molecular Dynamics (PIMD), Multiscale Simulation, Dense Phase, Interatomic Correlations
JOURNAL NAME:
Advances in Materials Physics and Chemistry,
Vol.16 No.10,
October
27,
2026
ABSTRACT: We present a multiscale molecular dynamics investigation of dense phases of argon, neon, and helium at 1 K, focusing on the role of quantum effects and interatomic correlations. Classical molecular dynamics (MD) simulations were employed for argon, while path integral molecular dynamics (PIMD) was used for neon and helium to capture quantum delocalization and zero-point energy (ZPE) effects. Interatomic interactions were modeled using HFD-type potentials for Ar, Ne, and He, with the Axilrod-Teller three-body potential added to account for many-body correlations. We calculated key properties including the radial distribution function, velocity autocorrelation function, mean squared displacement, and vibrational density of states. The results show a clear mass-dependent transition. Argon is well described by classical dynamics, neon exhibits intermediate behavior, and helium is dominated by strong quantum delocalization and markedly higher-frequency vibrational modes. Quantitatively, the zero-point energy (ZPE) values extracted from the thermodynamic estimator for the kinetic energy from the path integral molecular dynamics (PIMD) simulations decrease with increasing mass: ZPE (He) = 90.27 meV, ZPE (Ne) = 40.20 meV, and ZPE (Ar) ≈ 0 meV. Crucially, and counterintuitively, the relative contribution of three-body interactions is greatest for helium (50% of the total energy), compared to neon (15%) and argon (9%), as quantum delocalization increases the probability of multi-atom configurations. These findings underscore the critical interplay between quantum and many-body effects, which is essential for accurately modeling the microscopic behavior of dense atomic systems at cryogenic temperatures.