Relaxation contribution to Hessian: *RELAX

Directives controlling the calculation of the relaxation contributions (i.e. those from the response terms) to the different second-order molecular properties, appear in the *RELAX section.

.NOSELL

Do not use Sellers' method [157]. This method ensures that the error in the relaxation Hessian is quadratic in the error of the response equation solution, rather than linear. Mainly for debugging purposes.

.PRINT

READ (LUCMD,*) IPRINT

Set the print level in the calculation of the relaxation contributions. Read one more line containing print level. Default value is the value of IPRDEF from the general input module.

.SKIP

Skip the calculation of the relaxation contributions. This does not skip the solution of the response equations. This will give wrong results for a large number of second-order molecular properties. Mainly for debugging purposes.

.STOP

Stop the entire calculation after the calculation of the relaxation contributions to the requested properties. Mainly for debugging purposes.

.SYMTES

Calculate both the $ij$ and $ji$ elements of the relaxation Hessian to verify its Hermiticity or anti-Hermiticity (depending on the property being calculated). Mainly for debugging purposes.