Accession Number : ADA291297

Title :   Ab Initio Calculation of Vibrational Absorption and Circular Dichroism Spectra Using Density Functional Force Fields.

Descriptive Note : Final rept. Jan 93-Aug 94,

Corporate Author : ARMY RESEARCH LAB ABERDEEN PROVING GROUND MD

Personal Author(s) : Stephens, P. J. ; Devlin, F. J. ; Chabalowski, C. F. ; Frisch, M. J.

PDF Url : ADA291297

Report Date : FEB 1995

Pagination or Media Count : 33

Abstract : The unpolarized absorption and circular dichroism spectra of the fundamental vibrational transitions of the chiral molecule, 4-methyl-2-oxetanone, are calculated ab initio. Harmonic force fields are obtained using Density Functional Theory (DFT), MP2, and SCF methodologies and a 5S4P2D/3S2P (TZ2P) basis set. DFT calculations use the Local Spin Density Approximation (LSDA), BLYP, and Becke3LYP (B3LYP) density functionals. Mid-IR spectra predicted using LSDA, BLYP, and B3LYP force fields are of significantly different quality, the B3LYP force field yielding spectra in clearly superior, and overall excellent, agreement with experiment. The MP2 force field yields spectra in slightly worse agreement with experiment than the B3LYP force field. The SCF force field yields spectra in poor agreement with experiment.The basis set dependence of B3LYP force fields is also explored: the 6-31G* and TZ2P basis sets give very similar results while the 3-21G basis set yields spectra in substantially worse agreements with experiment. jg

Descriptors :   *VIBRATION, *SPECTRA, *ABSORPTION, *CIRCULAR, *DICHROISM, DENSITY, POLARIZATION, COMPUTATIONS, METHYL RADICALS, MOLECULES, QUANTUM THEORY, HARMONICS, SPINNING(MOTION), TRANSITIONS, INTERMEDIATE INFRARED RADIATION.

Subject Categories : Physical Chemistry
      Organic Chemistry
      Atomic and Molecular Physics and Spectroscopy
      Optics
      Quantum Theory and Relativity

Distribution Statement : APPROVED FOR PUBLIC RELEASE