TheoryLevel

TheoryLevel

Section Hamiltonian
Type integer

The calculations can be run with different "theory levels" that control how electrons are simulated. The default is kohn_sham. When hybrid or meta-GGA functionals are requested, through the XCFunctional variable, the default is generalized_kohn_sham.

Options:

• independent_particles:
  Particles will be considered as independent, i.e. as non-interacting. This mode is mainly used for testing purposes, as the code is usually much faster with independent_particles.
  
• hartree:
  Calculation within the Hartree method (experimental). Note that, contrary to popular belief, the Hartree potential is self-interaction-free. Therefore, this run mode will not yield the same result as kohn-sham without exchange-correlation.
  
• hartree_fock:
  This is the traditional Hartree-Fock scheme. Like the Hartree scheme, it is fully self-interaction-free.
  
• kohn_sham:
  This is the default density-functional theory scheme. Note that you can also use hybrid functionals in this scheme, but they will be handled the "DFT" way, i.e., solving the OEP equation. DFT+U (see DFTULevel) also runs within this scheme; it does not require generalized_kohn_sham.
  
• generalized_kohn_sham:
  This is similar to the kohn-sham scheme, except that this allows for nonlocal operators. This is the default mode to run hybrid functionals or meta-GGA functionals. It can be more convenient to use kohn-sham DFT within the OEP scheme to get similar (but not the same) results. Note that within this scheme you can use a correlation functional, or a hybrid functional (see XCFunctional). In the latter case, you will be following the quantum-chemistry recipe to use hybrids. DFT+U (see DFTULevel) can be combined with any theory level and yields the same result under kohn_sham and generalized_kohn_sham; it only requires generalized_kohn_sham when combined with a hybrid functional, so that the exact-exchange part is treated as a nonlocal operator.
  
• rdmft:
  (Experimental) Reduced Density Matrix functional theory.
  

 call parse_variable(namespace, 'TheoryLevel', default, ks%theory_level)