Directives for evaluation of molecular response functions

The directives in the following subsections may be included in the input to RESPONSE. THEY ARE ORGANIZED ACCORDING TO THE PROGRAM SECTION NAMES IN WHICH THEY APPEAR.

RESPONSE IS THE MOST GENERAL PART OF THE CODE FOR CALCULATING MANY DIFFERENT ELECTRONIC LINEAR, QUADRATIC, OR CUBIC MOLECULAR RESPONSE PROPERTIES BASED ON SCF, MCSCF OR CI WAVE FUNCTIONS, AS WELL AS KOHN-SHAM-BASED TIME-DEPENDENT DENSITY FUNCTIONAL THEORY. NO NUCLEAR CONTRIBUTIONS ARE ADDED.

IF THE FINAL WAVE FUNCTION FROM **WAVE FUNCTIONS WAS .CI, THEN A CONFIGURATION INTERACTION RESPONSE CALCULATION WILL BE PERFORMED. THIS IS EQUIVALENT TO A CI SUM-OVER-STATES CALCULATION OF RESPONSE PROPERTIES, BUT OF COURSE CALCULATED DIRECTLY WITHOUT DIAGONALIZATION OF THE FULL CI HAMILTONIAN MATRIX.

SOME OF THE SCF/MCSCF RESPONSE PROPERTIES CAN ALSO BE REQUESTED FROM **PROPERTIES INPUT MODULES. NOTE: FOR SUCH PROPERTIES YOU SHOULD REQUEST THEM EITHER HERE OR IN **PROPERTIES, OTHERWISE YOU WILL CALCULATE THEM TWICE! USUALLY THE OUTPUT IS NICEST IN THE **PROPERTIES MODULE (E.G. COLLECTED IN TABLES AND IN COMMONLY USED UNITS, MOST PROPERTIES ARE ONLY GIVEN IN ATOMIC UNITS IN RESPONSE), AND NUCLEAR CONTRIBUTIONS ARE INCLUDED IF RELEVANT. SOME SPECIFIC PROPERTIES, ESPECIALLY THOSE INVOLVING NUCLEAR DERIVATIVES, CAN ONLY BE CALCULATED VIA **PROPERTIES.

CALCULATIONS OF COUPLED CLUSTER RESPONSE PROPERTIES ARE PERFORMED BY DIFFERENT MODULES AND ARE DESCRIBED IN CHAPTER  ON COUPLED CLUSTER CALCULATIONS.

IN ADDITION, SOPPA (SECOND-ORDER POLARIZATION PROPAGATOR APPROXIMATION) OR SOPPA(CCSD) (SECOND ORDER POLARIZATION PROPAGATOR APPROXIMATION WITH COUPLED CLUSTER SINGLES AND DOUBLES AMPLITUDES) FOR THE CALCULATION OF LINEAR RESPONSE PROPERTIES AND EXCITATION ENERGIES WITH TRANSITION MOMENTS MAY BE REQUESTED IN THIS INPUT SECTION. THE CURRENT IMPLEMENTATION OF THE SOPPA METHOD IS DESCRIBED IN REF. [50] AND OF THE SOPPA(CCSD) METHOD IN REF. [52]. NOTE THAT A SOPPA CALCULATION REQUIRES THE KEYWORD .SOPPA, WHEREAS A SOPPA(CCSD) CALCULATION REQUIRES THE KEYWORD .SOPPA(CCSD).