# 11.15.2 $response Section and Operator Specification The specification of operators used in solving for response vectors is designed to be very flexible. The general form of the$response input section is given by

$response keyword_1 setting_1 keyword_2 setting_2 ... [operator_1_label, operator_1_origin] [operator_2_label, operator_2_origin] [operator_3_label, operator_3_origin] ...$end


where the keywords are those found in section 11.15.1 (with the exception of RESPONSE).

The specification of an operator is given within a line contained by [], where the first element is a label from table 11.4, and the second element is a label from table 11.5. Operator specifications may appear in any order. Response values are calculated for all possible permutations of operators and their components.

For the Cartesian moment operator, a third field within [] may be specified for the order of the expansion, entered as $(i,j,k)$. For example, the molecular response to the moment of order (2, 5, 4) with its origin at (0.2, 0.3, 0.4) a.u. can be found with the operator specification

[multipole, (0.2, 0.3, 0.4), (2, 5, 4)]