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29 lines
1.1 KiB
Fortran
29 lines
1.1 KiB
Fortran
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double precision function ec_lyp2(RhoA,RhoB,GA,GB,GAB)
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include 'constants.include.F'
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implicit none
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double precision, intent(in) :: RhoA,RhoB,GA,GB,GAB
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double precision :: Tol,caa,cab,cac,cad,cae,RA,RB,comega,cdelta,cLaa,cLbb,cLab,E
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ec_lyp2 = 0.d0
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Tol=1D-14
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E=2.718281828459045D0
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caa=0.04918D0
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cab=0.132D0
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cac=0.2533D0
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cad=0.349D0
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cae=(2D0**(11D0/3D0))*((3D0/10D0)*((3D0*(Pi**2D0))**(2D0/3D0)))
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RA = MAX(RhoA,0D0)
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RB = MAX(RhoB,0D0)
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IF ((RA.gt.Tol).OR.(RB.gt.Tol)) THEN
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IF ((RA.gt.Tol).AND.(RB.gt.Tol)) THEN
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comega = 1D0/(E**(cac/(RA+RB)**(1D0/3D0))*(RA+RB)**(10D0/3D0)*(cad+(RA+RB)**(1D0/3D0)))
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cdelta = (cac+cad+(cac*cad)/(RA+RB)**(1D0/3D0))/(cad+(RA+RB)**(1D0/3D0))
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cLaa = (cab*comega*RB*(RA-3D0*cdelta*RA-9D0*RB-((-11D0+cdelta)*RA**2D0)/(RA+RB)))/9D0
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cLbb = (cab*comega*RA*(-9D0*RA+(RB*(RA-3D0*cdelta*RA-4D0*(-3D0+cdelta)*RB))/(RA+RB)))/9D0
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cLab = cab*comega*(((47D0-7D0*cdelta)*RA*RB)/9D0-(4D0*(RA+RB)**2D0)/3D0)
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ec_lyp2 = -(caa*(cLaa*GA+cLab*GAB+cLbb*GB+cab*cae*comega*RA*RB*(RA**(8D0/3D0)+RB**(8D0/3D0))+(4D0*RA*RB)/(RA+RB+cad*(RA+RB)**(2D0/3D0))))
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endif
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endif
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end
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