Section Linear Response::Sternheimer
The terms to be considered in the variation of the Hamiltonian. The external potential (V_ext) is always considered. The default is to include also the exchange-correlation and Hartree terms, which fully takes into account local fields. Just hartree gives you the random-phase approximation (RPA). If you want to choose the exchange-correlation kernel, use the variable XCKernel. For kdotp and magnetic em_resp modes, or if TheoryLevel = independent_particles, the value V_ext_only is used and this variable is ignored.
Neither Hartree nor XC potentials included.
The variation of the Hartree potential only.
The exchange-correlation kernel (the variation of the
exchange-correlation potential) only.
call parse_variable(namespace, 'HamiltonianVariation', 3, ham_var)