44 THE VSCF PROGRAM (VSCF)

VSCF,options

The VSCF program is based on the Watson Hamiltonian

$$\hat{H} = \frac{1}{2} \sum_{\alpha\beta} ( \hat{J}_\alpha - ... ...um_i \frac{\partial^2}{\partial q_i^2} + V(q_1,\dots,q_{3N-6})$$ (20)

in which the potential energy surfaces, $V(q_1,\dots,q_{3N-6})$, are provided by the SURF module. Vibrational angular momentum terms (Coriolis coupling) are switched off by default. For solving the one-dimensional Schrödinger equation the DVR procedure of Hamilton and Light is used by default. Note that, the number of basis functions (distributed Gaussians) is determined by the grid NGRID of the potential and cannot be increased without changing the PES grid representation. In addition, 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).