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