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49 THE VSCF PROGRAM (VSCF)

VSCF,options

The VSCF program is based on the Watson Hamiltonian

$$\hat{H} = \frac{1}{2} \sum_{\alpha\beta} ( \hat{J}_\alpha - ... ...um_i \frac{\partial^2}{\partial q_i^2} + V(q_1,\dots,q_{3N-6})$$ (67)

in which the potential energy surfaces, $V(q_1,\dots,q_{3N-6})$, are provided by the SURF module. Vibrational angular momentum terms are switched off by default. Within the grid-based version of the program the one-dimensional Schrödinger equation is solved by the DVR procedure of Hamilton and Light. Note that, the number of basis functions (distributed Gaussians) is determined by the grid points of the potential and cannot be increased without changing the PES grid representation. In contrast to that the number of basis functions can be modified without restrictions in the polynomial based version. In all cases the basis is fixed to distributed Gaussians (DG). As VSCF calculations are extremely fast, these calculations cannot be restarted. For details see:


G. Rauhut, T. Hrenar, A Combined Variational and Perturbational Study on the Vibrational Spectrum of P$_2$F$_4$, Chem. Phys. 346, 160 (2008).

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