Q. Levels of accuracy in the SAC/SAC-CI calculations

 

A. Levels of accuracy can be controlled by the options LevelOne / LevelTwo / LevelThree, which are in order of increasing the accuracy. These define energy thresholds for the perturbation selection of linked double-excitation operators in the SAC/SAC-CI wave functions. LevelThree is set as the default. In LevelOne, EThreS2=1*10**(-5), EThreR2=1*10**(-6) a.u., in LevelTwo, EThreS2=5*10**(-6), EThreR2=5*10**(-7) a.u., and in LevelThree, EThreS2=1*10**(-6), EThreR2=1*10**(-7) a.u..