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52.6 Linear combinations of normal coordinates

LINCOMB,options

The LINCOMB directive allows for the calculation of linear combinations of normal coordinates for the expansion of the potential. This is realized by 2x2 Jacobi rotations. At most 3N-6/2 rotations can be provided in the input. Using an angle of 45$^o$ between the degenerate modes of non-Abelian molecules avoids symmetry breaking in the subsequent VSCF and VCI calculations.

NM1=n, NM2=m

Denotes the normal coordinates to be rotated.

ANGLE=value

Rotation angle in degree.

LOCAL=value

LOCAL=1 localizes the normal coordinates of the CH-stretchings. Note that this destroys symmetry of these modes. Usually localization has strong impact on subsequent VSCF calculations. LOCAL=2 localizes the normal coordinates of a molecular cluster to the contributing entities. This localization scheme localizes within the individual irreps, which usually leads to a very faint localization. Switching symmetry off by MPG=1 in the SURF program leads to a much stronger localization. LOCAL=3 is a combination of LOCAL=1 and LOCAL=2.

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