2021-02-12 16:47:40 +01:00
|
|
|
subroutine ULYP_gga_correlation_energy(nGrid,weight,rho,drho,Ec)
|
|
|
|
|
|
|
|
|
|
! Compute unrestricted LYP GGA correlation energy
|
|
|
|
|
|
|
|
|
|
implicit none
|
|
|
|
|
|
|
|
|
|
include 'parameters.h'
|
|
|
|
|
|
|
|
|
|
! Input variables
|
|
|
|
|
|
|
|
|
|
integer,intent(in) :: nGrid
|
|
|
|
|
double precision,intent(in) :: weight(nGrid)
|
|
|
|
|
double precision,intent(in) :: rho(nGrid,nspin)
|
|
|
|
|
double precision,intent(in) :: drho(ncart,nGrid,nspin)
|
|
|
|
|
|
|
|
|
|
! Local variables
|
|
|
|
|
|
|
|
|
|
integer :: iG
|
|
|
|
|
double precision :: ra,rb,r
|
|
|
|
|
double precision :: ga,gab,gb,g
|
|
|
|
|
|
|
|
|
|
double precision :: a,b,c,d
|
|
|
|
|
double precision :: Cf,omega,delta
|
|
|
|
|
|
|
|
|
|
! Output variables
|
|
|
|
|
|
|
|
|
|
double precision :: Ec(nsp)
|
|
|
|
|
|
|
|
|
|
! Parameters of the functional
|
|
|
|
|
|
|
|
|
|
a = 0.04918d0
|
|
|
|
|
b = 0.132d0
|
|
|
|
|
c = 0.2533d0
|
|
|
|
|
d = 0.349d0
|
|
|
|
|
|
|
|
|
|
Cf = 3d0/10d0*(3d0*pi**2)**(2d0/3d0)
|
|
|
|
|
|
|
|
|
|
! Initialization
|
|
|
|
|
|
|
|
|
|
Ec(:) = 0d0
|
|
|
|
|
|
|
|
|
|
do iG=1,nGrid
|
|
|
|
|
|
|
|
|
|
ra = max(0d0,rho(iG,1))
|
|
|
|
|
rb = max(0d0,rho(iG,2))
|
|
|
|
|
r = ra + rb
|
|
|
|
|
|
|
|
|
|
if(r > threshold) then
|
|
|
|
|
|
2021-02-13 22:31:46 +01:00
|
|
|
ga = drho(1,iG,1)*drho(1,iG,1) + drho(2,iG,1)*drho(2,iG,1) + drho(3,iG,1)*drho(3,iG,1)
|
|
|
|
|
gb = drho(1,iG,2)*drho(1,iG,2) + drho(2,iG,2)*drho(2,iG,2) + drho(3,iG,2)*drho(3,iG,2)
|
2021-02-12 16:47:40 +01:00
|
|
|
gab = drho(1,iG,1)*drho(1,iG,2) + drho(2,iG,1)*drho(2,iG,2) + drho(3,iG,1)*drho(3,iG,2)
|
2021-02-13 22:31:46 +01:00
|
|
|
g = ga + 2d0*gab + gb
|
2021-02-12 16:47:40 +01:00
|
|
|
|
|
|
|
|
omega = exp(-c*r**(-1d0/3d0))/(1d0 + d*r**(-1d0/3d0))*r**(-11d0/3d0)
|
|
|
|
|
delta = c*r**(-1d0/3d0) + d*r**(-1d0/3d0)/(1d0 + d*r**(-1d0/3d0))
|
|
|
|
|
|
|
|
|
|
Ec(2) = Ec(2) - weight(iG)*4d0*a/(1d0 + d*r**(-1d0/3d0))*ra*rb/r &
|
|
|
|
|
- weight(iG)*a*b*omega*ra*rb*( &
|
|
|
|
|
2d0**(11d0/3d0)*Cf*(ra**(8d0/3d0) + rb**(8d0/3d0)) &
|
|
|
|
|
+ (47d0/18d0 - 7d0*delta/18d0)*g &
|
|
|
|
|
- (5d0/2d0 - delta/18d0)*(ga + gb) &
|
|
|
|
|
- (delta - 11d0)/9d0*(ra/r*ga + rb/r*gb) ) &
|
|
|
|
|
- weight(iG)*a*b*omega*( &
|
|
|
|
|
- 2d0*r**2/3d0*g &
|
|
|
|
|
+ (2d0*r**2/3d0 - ra**2)*gb &
|
|
|
|
|
+ (2d0*r**2/3d0 - rb**2)*ga )
|
|
|
|
|
|
|
|
|
|
end if
|
|
|
|
|
|
|
|
|
|
end do
|
|
|
|
|
|
|
|
|
|
end subroutine ULYP_gga_correlation_energy
|
