mirror of
https://github.com/pfloos/quack
synced 2024-12-26 14:23:38 +01:00
123 lines
2.8 KiB
Fortran
123 lines
2.8 KiB
Fortran
|
subroutine UPW92_lda_correlation_energy(nGrid,weight,rho,Ec)
|
||
|
|
|
||
|
|
! Compute unrestricted PW92 LDA 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)
|
||
|
|
|
||
|
|
! Local variables
|
||
|
|
|
||
|
|
integer :: iG
|
||
|
|
double precision :: ra,rb,r,rs,x,z
|
||
|
|
double precision :: A_p,a1_p,b1_p,b2_p,b3_p,b4_p
|
||
|
|
double precision :: A_f,a1_f,b1_f,b2_f,b3_f,b4_f
|
||
|
|
double precision :: A_a,a1_a,b1_a,b2_a,b3_a,b4_a
|
||
|
|
|
||
|
|
double precision :: ec_z,ec_p,ec_f,ec_a
|
||
|
|
double precision :: fz,d2fz
|
||
|
|
|
||
|
|
! Output variables
|
||
|
|
|
||
|
|
double precision :: Ec(nsp)
|
||
|
|
|
||
|
|
! Parameters of the functional
|
||
|
|
|
||
|
|
A_p = 0.031091d0
|
||
|
|
a1_p = 0.21370d0
|
||
|
|
b1_p = 7.5957d0
|
||
|
|
b2_p = 3.5876d0
|
||
|
|
b3_p = 1.6382d0
|
||
|
|
b4_p = 0.49294d0
|
||
|
|
|
||
|
|
A_f = 0.015545d0
|
||
|
|
a1_f = 0.20548d0
|
||
|
|
b1_f = 14.1189d0
|
||
|
|
b2_f = 6.1977d0
|
||
|
|
b3_f = 3.3662d0
|
||
|
|
b4_f = 0.62517d0
|
||
|
|
|
||
|
|
A_a = 0.016887d0
|
||
|
|
a1_a = 0.11125d0
|
||
|
|
b1_a = 10.357d0
|
||
|
|
b2_a = 3.6231d0
|
||
|
|
b3_a = 0.88026d0
|
||
|
|
b4_a = 0.49671d0
|
||
|
|
|
||
|
|
! Initialization
|
||
|
|
|
||
|
|
Ec(:) = 0d0
|
||
|
|
|
||
|
|
do iG=1,nGrid
|
||
|
|
|
||
|
|
ra = max(0d0,rho(iG,1))
|
||
|
|
rb = max(0d0,rho(iG,2))
|
||
|
|
|
||
|
|
! alpha-alpha contribution
|
||
|
|
|
||
|
|
if(ra > threshold) then
|
||
|
|
|
||
|
|
rs = (4d0*pi*ra/3d0)**(-1d0/3d0)
|
||
|
|
|
||
|
|
ec_f = b1_f*sqrt(rs) + b2_f*rs + b3_f*rs**(3d0/2d0) + b4_f*rs**2
|
||
|
|
ec_f = -2d0*A_f*(1d0 + a1_f*rs)*log(1d0 + 1d0/(2d0*A_f*ec_f))
|
||
|
|
|
||
|
|
Ec(1) = Ec(1) + weight(iG)*ec_f*ra
|
||
|
|
|
||
|
|
end if
|
||
|
|
|
||
|
|
! alpha-beta contribution
|
||
|
|
|
||
|
|
if(ra > threshold .or. rb > threshold) then
|
||
|
|
|
||
|
|
r = ra + rb
|
||
|
|
rs = (4d0*pi*r/3d0)**(-1d0/3d0)
|
||
|
|
z = (ra - rb)/r
|
||
|
|
x = sqrt(rs)
|
||
|
|
|
||
|
|
fz = (1d0 + z)**(4d0/3d0) + (1d0 - z)**(4d0/3d0) - 2d0
|
||
|
|
fz = fz/(2d0*(2d0**(1d0/3d0) - 1d0))
|
||
|
|
|
||
|
|
d2fz = 4d0/(9d0*(2**(1d0/3d0) - 1d0))
|
||
|
|
|
||
|
|
ec_p = b1_p*sqrt(rs) + b2_p*rs + b3_p*rs**(3d0/2d0) + b4_p*rs**2
|
||
|
|
ec_p = -2d0*A_p*(1d0 + a1_p*rs)*log(1d0 + 1d0/(2d0*A_p*ec_p))
|
||
|
|
|
||
|
|
ec_f = b1_f*sqrt(rs) + b2_f*rs + b3_f*rs**(3d0/2d0) + b4_f*rs**2
|
||
|
|
ec_f = -2d0*A_f*(1d0 + a1_f*rs)*log(1d0 + 1d0/(2d0*A_f*ec_f))
|
||
|
|
|
||
|
|
ec_a = b1_a*sqrt(rs) + b2_a*rs + b3_a*rs**(3d0/2d0) + b4_a*rs**2
|
||
|
|
ec_a = +2d0*A_a*(1d0 + a1_a*rs)*log(1d0 + 1d0/(2d0*A_a*ec_a))
|
||
|
|
|
||
|
|
ec_z = ec_p + ec_a*fz/d2fz*(1d0-z**4) + (ec_f - ec_p)*fz*z**4
|
||
|
|
|
||
|
|
Ec(2) = Ec(2) + weight(iG)*ec_z*r
|
||
|
|
|
||
|
|
end if
|
||
|
|
|
||
|
|
! beta-beta contribution
|
||
|
|
|
||
|
|
if(rb > threshold) then
|
||
|
|
|
||
|
|
rs = (4d0*pi*rb/3d0)**(-1d0/3d0)
|
||
|
|
x = sqrt(rs)
|
||
|
|
|
||
|
|
ec_f = b1_f*sqrt(rs) + b2_f*rs + b3_f*rs**(3d0/2d0) + b4_f*rs**2
|
||
|
|
ec_f = -2d0*A_f*(1d0 + a1_f*rs)*log(1d0 + 1d0/(2d0*A_f*ec_f))
|
||
|
|
|
||
|
|
Ec(3) = Ec(3) + weight(iG)*ec_f*rb
|
||
|
|
|
||
|
|
end if
|
||
|
|
|
||
|
|
end do
|
||
|
|
|
||
|
|
Ec(2) = Ec(2) - Ec(1) - Ec(3)
|
||
|
|
|
||
|
|
end subroutine UPW92_lda_correlation_energy
|