Molecular-dynamics study of the dynamical excitations in commensurate monolayer films of nitrogen molecules on graphite: A test of the corrugation in the nitrogen-graphite potential

Flemming Yssing Hansen, Ludwig Walter Bruch

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Abstract

The dynamical excitations in a commensurate monolayer solid of N2 molecules adsorbed on graphite have been studied using molecular-dynamics simulations. Velocity and rotational correlation functions as well as coherent intermediate scattering functions and dynamical structure factors have been calculated at several temperatures and wave vectors. Effects of out-of-plane motions and the formation of pinwheel-like structural elements associated with the orientational-disorder transition are observed both in the equilibrium order parameters and in the time-correlation functions. The calculated temperature dependence of the Brillouin-zone-center frequency gap in the acoustic phonon branches up to the melting point agrees well with the experimental observations and gives strong support to a model of the substrate corrugation energy. Diffusive motion in the fluid just above the melting point has been demonstrated from the time dependence of the mean-square displacement of the molecules and the two-dimensional diffusion coefficient is estimated to be 2–3×10-5 cm2/s at 75–80 K.
Original languageEnglish
JournalPhysical Review B
Volume51
Issue number4
Pages (from-to)2515-2536
ISSN2469-9950
DOIs
Publication statusPublished - 1995

Bibliographical note

Copyright (1995) by the American Physical Society.

Keywords

  • PHASE-DIAGRAM
  • MONTE-CARLO
  • N-2
  • TRANSITION
  • CONSTRAINT
  • SUBMONOLAYER KRYPTON
  • SIMULATION
  • BASAL-PLANE
  • N2
  • HEAT

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