Journal article
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
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.
Language: | English |
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Year: | 1995 |
Pages: | 2515-2536 |
ISSN: | 1550235x , 24699950 , 10953795 and 01631829 |
Types: | Journal article |
DOI: | 10.1103/PhysRevB.51.2515 |