Molecular dynamics ensemble, equation of state, and ergodicity

Journal Article · Mon Jan 01 04:00:00 EST 2001 · Physical Review E

DOI:https://doi.org/10.1103/PhysRevE.63.011106· OSTI ID:40205347

Wood, William W; Erpenbeck, Jerome J; Baker, George A; Johnson, J D

The variant of the NVE ensemble known as the molecular dynamics ensemble was recently redefined by Ray and Zhang [Phys. Rev. E 59, 4781 (1999)] to include the specification of a time invariant G (a function of phase and, explicitly, the time) in addition to the total linear momentum M. We reformulate this ensemble slightly as the NVEMR ensemble, in which R/N is the center-of-mass position, and consider the equation of state of the hard-sphere system in this ensemble through both the virial function and the Boltzmann entropy. We test the quasiergodic hypothesis by a comparison of old molecular dynamics and Monte Carlo results for the compressibility factor of the 12-particle, hard-disk systems. The virial approach, which had previously been found to support the hypothesis in the NVEM ensemble, remains unchanged in the NVEMR ensemble. The entropy S approach depends on whether S is defined through the phase integral over the energy sphere or the energy shell, the parameter {theta} being 0 or 1, respectively. The ergodic hypothesis is found to be supported for {theta}=0 but not for {theta}=1.

• Sponsoring Organization: (US)
• OSTI ID: 40205347
• Journal Information: Physical Review E, Journal Name: Physical Review E Journal Issue: 1 Vol. 63; ISSN 1063-651X
• Publisher: The American Physical Society
• Country of Publication: United States
• Language: English

Related Subjects

71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
COMPRESSIBILITY
ENTROPY
ERGODIC HYPOTHESIS
HYPOTHESIS
LINEAR MOMENTUM
SPECIFICATIONS