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153 lines
5.0 KiB
Fortran
153 lines
5.0 KiB
Fortran
!****************************************************************************
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subroutine ESRC_MD_LDAERF (mu,rho_a,rho_b,dospin,e)
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!*****************************************************************************
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! Short-range spin-dependent LDA correlation functional with multideterminant reference
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! for OEP calculations from Section V of
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! Paziani, Moroni, Gori-Giorgi and Bachelet, PRB 73, 155111 (2006)
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!
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! Input: rhot : total density
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! rhos : spin density
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! mu : Interation parameter
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! dospin : use spin density
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!
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! Ouput: e : energy
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!
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! Created: 26-08-11, J. Toulouse
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!*****************************************************************************
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implicit none
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double precision, intent(in) :: rho_a,rho_b,mu
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logical, intent(in) :: dospin
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double precision, intent(out):: e
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double precision :: e1
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double precision :: rhoa,rhob
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double precision :: rhot, rhos
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rhoa=max(rho_a,1.0d-15)
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rhob=max(rho_b,1.0d-15)
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rhot = rhoa + rhob
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rhos = rhoa - rhob
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call ec_only_lda_sr(mu,rho_a,rho_b,e1)
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if(isnan(e1))then
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print*,'e1 is NaN'
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print*,mu,rho_a,rho_b
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stop
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endif
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call DELTA_LRSR_LDAERF (rhot,rhos,mu,dospin,e)
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if(isnan(e))then
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print*,'e is NaN'
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print*,mu,rhot,rhos
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stop
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endif
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e = e1 + e
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end
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!****************************************************************************
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subroutine DELTA_LRSR_LDAERF (rhot,rhos,mu,dospin,e)
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!*****************************************************************************
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! LDA approximation to term Delta_(LR-SR) from Eq. 42 of
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! Paziani, Moroni, Gori-Giorgi and Bachelet, PRB 73, 155111 (2006)
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!
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! Input: rhot : total density
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! rhos : spin density
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! mu : Interation parameter
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! dospin : use spin density
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!
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! Ouput: e : energy
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!
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! Warning: not tested for z != 0
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!
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! Created: 26-08-11, J. Toulouse
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!*****************************************************************************
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implicit none
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double precision rhot, rhos, mu
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logical dospin
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double precision e
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double precision f13, f83, pi, rsfac, alpha2
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double precision rs, rs2, rs3
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double precision rhoa, rhob, z, z2, onepz, onemz, zp, zm, phi8
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double precision g0f, g0s
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double precision bd2, bd3
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double precision c45, c4, c5
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double precision bc2, bc4, bc3t, bc5t, d0
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double precision delta2,delta3,delta4,delta5,delta6
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double precision delta
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parameter(f13 = 0.333333333333333d0)
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parameter(f83 = 2.6666666666666665d0)
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parameter(pi = 3.141592653589793d0)
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parameter(rsfac = 0.620350490899400d0)
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parameter(alpha2 = 0.2715053589826032d0)
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rs = rsfac/(rhot**f13)
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rs2 = rs*rs
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rs3 = rs2*rs
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! Spin-unpolarized case
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if (.not.dospin) then
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z = 0.d0
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! Spin-polarized case
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else
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rhoa=max((rhot+rhos)*.5d0,1.0d-15)
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rhob=max((rhot-rhos)*.5d0,1.0d-15)
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z=min((rhoa-rhob)/(rhoa+rhob),0.9999999999d0)
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endif
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z2=z*z
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bd2=dexp(-0.547d0*rs)*(-0.388d0*rs+0.676*rs2)/rs2
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bd3=dexp(-0.31d0*rs)*(-4.95d0*rs+rs2)/rs3
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onepz=1.d0+z
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onemz=1.d0-z
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phi8=0.5d0*(onepz**f83+onemz**f83)
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zp=onepz/2.d0
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zm=onemz/2.d0
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c45=(zp**2)*g0s(rs*zp**(-f13))+(zm**2)*g0s(rs*zm**(-f13))
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c4=c45+(1.d0-z2)*bd2-phi8/(5.d0*alpha2*rs2)
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c5=c45+(1.d0-z2)*bd3
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bc2=-3.d0*(1-z2)*(g0f(rs)-0.5d0)/(8.d0*rs3)
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bc4=-9.d0*c4/(64.d0*rs3)
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bc3t=-(1-z2)*g0f(rs)*(2.d0*dsqrt(2.d0)-1)/(2.d0*dsqrt(pi)*rs3)
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bc5t = -3.d0*c5*(3.d0-dsqrt(2.d0))/(20.d0*dsqrt(2.d0*pi)*rs3)
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d0=(0.70605d0+0.12927d0*z2)*rs
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delta2=0.073867d0*(rs**(1.5d0))
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delta3=4*(d0**6)*bc3t+(d0**8)*bc5t;
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delta4=4*(d0**6)*bc2+(d0**8)*bc4;
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delta5=(d0**8)*bc3t;
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delta6=(d0**8)*bc2;
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delta=(delta2*(mu**2)+delta3*(mu**3)+delta4*(mu**4)+delta5*(mu**5)+delta6*(mu**6))/((1+(d0**2)*(mu**2))**4)
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! multiply by rhot to get energy density
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e=delta*rhot
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end
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!*****************************************************************************
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double precision function g0s(rs)
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!*****************************************************************************
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! g"(0,rs,z=1) from Eq. 32 of
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! Paziani, Moroni, Gori-Giorgi and Bachelet, PRB 73, 155111 (2006)
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!
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! Created: 26-08-11, J. Toulouse
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!*****************************************************************************
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implicit none
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double precision rs
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double precision rs2, f53, alpha2
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parameter(f53 = 1.6666666666666667d0)
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parameter(alpha2 = 0.2715053589826032d0)
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rs2=rs*rs
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g0s=(2.d0**f53)*(1.d0-0.02267d0*rs)/((5.d0*alpha2*rs2)*(1.d0+0.4319d0*rs+0.04d0*rs2))
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end
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