34.2.21 Optimizing energy variables (VARIABLE)

VARIABLE,name;

Defines a variable name which holds the energy value to be optimized in using finite differences. By default, this is ENERGY(1) as set by the most recent program. Other variables which can be used are

ENERGY(i)

holds last energy for state i.

ENERGR(i)

holds last reference energy for state i.

ENERGD(i)

holds last Davidson corrected energy for state i.

ENERGP(i)

holds last Pople corrected energy for state i.

ENERGC

holds CCSD (QCI, BCCD) energy in CCSD(T) [QCI(T), BCCD(T)] calculations (single state optimization).

ENERGT(1)

holds CCSD(T) energy in CCSD(T) calculations (single state)

ENERGT(2)

holds CCSD[T] energy in CCSD(T) calculations (single state).

ENERGT(3)

holds CCSD-T energy in CCSD(T) calculations (single state).

These variables are set automatically by the CI and/or CCSD programs. It is the user's responsibility to use the correct variable name; an error exit occurs if the specified variable has not been defined by the last program or the user.

Note: The use of the VARIABLE option triggers NUMERICAL, so optimization can be very inefficient!