Dw. Dean et Jr. Chelikowsky, FIRST PRINCIPLES CALCULATION OF THE THERMODYNAMIC PROPERTIES OF SILICON CLUSTERS, Theoretical chemistry accounts, 99(1), 1998, pp. 18-28
The thermodynamic properties of Si clusters are calculated using first
principles quantum methods combined with molecular dynamics for simul
ating the trajectories of clusters. A plane wave basis is used with ab
initio pseudo potentials and the local density approximation for dete
rmining the electronic energies and forces. Langevin molecular dynamic
s simulates thermal contact with a constant temperature reservoir. Vib
rational spectra, moments of inertia, anharmonic corrections, and free
energies are predicted for Si-2 through Si-5. The translational contr
ibution is based on the ideal gas limit. The rotation contribution is
approximated using a classical rigid rotator. Vibrational modes are de
termined from the dynamical matrix in the harmonic approximation. Corr
ections due to anharmonicity and coupling between rotational and vibra
tional modes are fit from the molecular dynamics simulations.