Q. Dimension (number of the excitation operators) of the SAC/SAC-CI calculations

 

A. Dimension of the SAC/SAC-CI calculations, number of the excitation operators, depends on the threshold of the perturbation selection, LevelOne / LevelTwo / LevelThree. Before doing the whole SAC-CI calculations, one can check the size of the calculations by using the option "SelecCISonly". We note that a calculation more than 400,000 linked operators would take more than a week in ordinary work stations (for example, HP DS25/alpha 1.0GHz). To reduce the dimension, you can try the lower level of selection or reduce number of solution in the SAC-CI calculation