Accession Number:

ADA284305

Title:

Theoretical Prediction of Vibrational Circular Dichroism Spectra of R- Glyceraldehyde, R-Erythrose, and R-Threose. 2. Development of a Procedure to Scale the Force Constant Matrix Expressed in Terms of Internal Coordinates

Descriptive Note:

Final rept. May-Oct 1992

Corporate Author:

BATTELLE MEMORIAL INST RESEARCH TRIANGLE PARK NC

Report Date:

1993-11-01

Pagination or Media Count:

45.0

Abstract:

A very important objective of the Detection Directorate at the U.S. Army Edgewood Research, Development and Engineering Center is the remote detection of biological materials in the field. One line of thinking, currently being followed, is the recognition that sugars are distinguishing features of biological materials. In Part I of this study, the theoretical prediction of the vibrational circular dichroism VCD of the 3 and 4 carbon sugars R- glyceraldehyde, R-erythrose, and R-threose is considered. The calculational procedure used involves determination of the frequencies corresponding to the normal modes of vibration. Since calculated frequencies at the Hartree-Fock level are typically 10 too high, some form of scaling of the frequencies or the force constant matrix is required for quantitative agreement with experimental measurements. In Part II of this study, a scaling method is described, and three key FORTRAN computer programs are presented. Basically, the force constant matrix in internal coordinates at the 6-31G HF level of calculation is scaled to the calculated 6-31G MP2 level of calculation. The force constant matrix in terms of Cartesian coordinates can be determined from a matrix transformation, originally shown by Pulay, involving the force constant matrix in terms of internal coordinates. The scaling constant for each off-diagonal element of the force constant matrix was determined by using the geometric mean Q sub ij Q sub iQ sub j12 of the diagonal scaling constants Q sub i and Q sub j. Vibrational circular dichroism, Scaling of force constant matrix.

Subject Categories:

  • Physical Chemistry
  • Infrared Detection and Detectors

Distribution Statement:

APPROVED FOR PUBLIC RELEASE