HSE functional

[mguidon]

Hi.

The HSE functional is a hybrid functional. It consists of screened
exact Hartree-Fock exchange and two GGA-functionals (PBE and hole-
averaged screened PBE functional). The keywords are (see /tests/QS/
regtest-hybrid/NE-hybrid-HSE06-lda.inp):

&XC_FUNCTIONAL
  &XWPBE
     SCALE_X -0.25
     SCALE_X0 1.0
     OMEGA 0.11
   &END
   &PBE
      SCALE_X 0.0
      SCALE_C 1.0
   &END PBE
 &END XC_FUNCTIONAL
 &HF
    EPS_SCHWARZ 1.0E-10
    MAX_MEMORY  10
    FRACTION 0.25
    SCREENING_TYPE SHORTRANGE
    OMEGA 0.11
  &END

As in the case of B3LYP the functional is quite expensive since exact
exchange has to be calculated. However, the keyword OMEGA decreases
the cost for the Hartree-Fock part because it results in a better
screening. To get accurate results it is recommended to use OMEGA
values within the range of 0.1 and 0.2. (Higher value means better
screening means faster execution). In the current version, analytical
derivatives up to second order are implemented which means that forces/
stresses are available.
As with all calculations including Hartree-Fock exchange you need an
up-to-date g95 compiler together with the libint-library in order to
run cp2k.

Cheers

Manuel Guidon