:term:`CFOUR_HBAR <CFOUR_HBAR (CFOUR)>`
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      This keyword determines which action is taken by the linear response program. ON (=1) the full effective Hamiltonian is calculated and written to disk; OFF (=0) the "lambda" linear response equations are solved.

      * **Type**: :ref:`boolean <op_c_boolean>`
      * **Default**: false

