mirror of
https://github.com/pfloos/quack
synced 2024-06-15 01:35:29 +02:00
60 lines
1.5 KiB
Fortran
60 lines
1.5 KiB
Fortran
subroutine RB88_gga_exchange_individual_energy(nGrid,weight,rhow,drhow,rho,drho,Ex)
|
|
|
|
! Compute restricted Becke's GGA indivudal energy
|
|
|
|
implicit none
|
|
include 'parameters.h'
|
|
|
|
! Input variables
|
|
|
|
integer,intent(in) :: nGrid
|
|
double precision,intent(in) :: weight(nGrid)
|
|
double precision,intent(in) :: rhow(nGrid)
|
|
double precision,intent(in) :: drhow(ncart,nGrid)
|
|
double precision,intent(in) :: rho(nGrid)
|
|
double precision,intent(in) :: drho(ncart,nGrid)
|
|
|
|
! Local variables
|
|
|
|
integer :: iG
|
|
double precision :: beta
|
|
double precision :: r,rI,g,x
|
|
double precision :: ex_p,dexdr_p
|
|
|
|
! Output variables
|
|
|
|
double precision,intent(out) :: Ex
|
|
|
|
! Coefficients for B88 GGA exchange functional
|
|
|
|
beta = 0.0042d0
|
|
|
|
! Compute GGA exchange matrix in the AO basis
|
|
|
|
Ex = 0d0
|
|
|
|
do iG=1,nGrid
|
|
|
|
r = max(0d0,0.5d0*rhow(iG))
|
|
rI = max(0d0,0.5d0*rho(iG))
|
|
|
|
if(r > threshold .or. rI > threshold) then
|
|
|
|
g = 0.25d0*(drho(1,iG)**2 + drho(2,iG)**2 + drho(3,iG)**2)
|
|
x = sqrt(g)/r**(4d0/3d0)
|
|
|
|
dexdr_p = 4d0/3d0*r**(1d0/3d0)*(CxLDA - beta*g**(3d0/4d0)/r**2) &
|
|
+ 2d0*beta*g**(3d0/4d0)/r**(5d0/3d0) &
|
|
- 2d0*3d0/4d0*beta*g**(-1d0/4d0)/r**(2d0/3d0)
|
|
|
|
ex_p = CxLDA*r**(4d0/3d0) &
|
|
- weight(iG)*beta*x**2*r**(4d0/3d0)/(1d0 + 6d0*beta*x*asinh(x))
|
|
|
|
Ex = Ex + weight(iG)*(ex_p*rI + dexdr_p*r*rI - dexdr_p*r*r)
|
|
|
|
end if
|
|
|
|
end do
|
|
|
|
end subroutine RB88_gga_exchange_individual_energy
|