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176. NORCRD: Short XYZ Version
by William D. Gwinn, Department of Chemistry, University of California, Berkeley, California 94720 This program calculates the normal coordinates and vibrational frequencies of a molecule. The kinetic energy and potential energy matrices are set up in Cartesian coordinates of each atom. The rotation and translation are not separated. The Cartesian coordinates are later mass weighted. The kinetic energy matrix then becomes a unit matrix and thus does not appear in the program. The potential energy matrix is diagonalized, and the vibrational frequencies are found from each eigenvalue. The eigenvectors are directly the normal coordinates in mass weighted Cartesian coordinates. The normal coordinate in terms of Cartesian coordinates is also given. The program gives eigenvalues and frequencies of zero for each translation and rotation and free internal rotation.These are not printed out. Negative eigenvalues are also trapped but give an error message. These should never occur, and the trap should probably be removed. This version of the program requires that the structure of the molecule under consideration be entered as Cartesian coordinates. FORTRAN IV (CDC 6000 Series) Lines of Code: 689 Recommended Citation: W. D. Gwinn, QCPE 11, 176 (1971). |