VIBRATIONAL FREQUENCIES OF DIATOMIC-MOLECULES FROM CAR AND PARRINELLOMOLECULAR-DYNAMICS

The vibrational frequency of selected diatomic molecules (H-2, N-2, F- 2, HF, CO) has been calculated from Car-Parrinello molecular dynamics. The associated electronic energies have been obtained within the Born -Oppenheimer approximation by using the local density functional schem e where plane waves and pseudopotentials are used. Our vibrational fre quency results, extrapolated to zero effective fictitious mass values, are in good agreement with the experimental values for H-2, N-2, HF a nd CO, whereas for F-2 our calculated value is larger. The optimized b ond lengths and the harmonic vibrational frequencies obtained by a loc al density functional scheme with plane waves have been compared with other theoretical methods (Hartree-Fock, MP2, CCSD(T), DFT using Gauss ian basis sets). There is good agreement between the LDA procedure usi ng plane-wave or Gaussian-type orbital basis sets. (C) 1997 Elsevier S cience B.V.