The molecular gradient module is usually called from within the geometry optimization module.
If activated the calculation of the SL and SS two-electron integral contributions to the gradient is skipped if their contribution is estimated to be small. An “empirical” estimate of the norms of the LS and SS two-electron gradients based on the norm of the LL two-electron gradient. If deactivated all contributions to gradient are calculated and if activated then only “necessary” contributions are calculated.
Which means that screening is turned off by default. This is due to an enormous demand of memory.
A print level of less than 3 gives only the total gradient. Print levels from 3+ gives individual contributions to the gradient (kinetic energy gradient, nuclear attraction gradient etc.). Print levels of 5+ print some matrices, and 10+ give massive output!
Calculate the molecular gradient using numerical differentiation.
Default: Analytical evaluation if implemented.