123 lines
3.9 KiB
Fortran
123 lines
3.9 KiB
Fortran
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!=======================================================================
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!
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MODULE DELTA_KIN
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!
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USE ACCURACY_REAL
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!
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CONTAINS
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!
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!------ 1) 3D case --------------------------------------------
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!
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!=======================================================================
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!
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SUBROUTINE DELTA_KIN_3D(EC_TYPE,IMODE,IDERIV,RS,T,I_DE,DT,DT2)
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!
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! This subroutine computes delta_t and delta_t2 values for 3D systems
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!
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!
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! References: (1) J. Toulouse, Phys. Rev. B 72, 035117 (2005)
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!
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! They are defined, in terms of the kinetic energy, as
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!
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! < t > - < t >
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! 0
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! delta_t = ----------------
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!
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! < t >
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! 0
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!
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!
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! 2 2
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! < t > - < t >
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! 0
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! delta_t2 = ----------------
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! 2
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! < t >
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! 0
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!
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!
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! Input parameters:
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!
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! * EC_TYPE : type of correlation energy functional
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! * IMODE : choice of parameters
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! IMODE = 1 : no spin polarization
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! IMODE = 2 : fully spin-polarized
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! * IDERIV : type of n_point formula used for derivation (n = IDERIV)
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! * RS : Wigner-Seitz radius of electron (in units of a_0)
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! * T : temperature (SI)
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! * I_DE : type of parametrization of delta_t2
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! I_DE = 1 : RPA
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! I_DE = 2 : GW
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! I_DE = 3 : Gori-Giorgi and Ziesche
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!
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!
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! Output parameters:
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!
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! * DT : delta_t
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! * DT2 : delta_t2
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!
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!
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!
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! Author : D. Sébilleau
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!
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! Last modified : 30 Oct 2020
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!
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!
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!
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USE REAL_NUMBERS, ONLY : TWO,FIVE,THIRD
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USE FERMI_AU, ONLY : EF_AU
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!
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USE CORRELATION_ENERGIES
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!
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IMPLICIT NONE
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!
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CHARACTER (LEN = 6) :: EC_TYPE
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!
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INTEGER, INTENT(IN) :: IMODE,IDERIV,I_DE
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!
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REAL (WP), INTENT(IN) :: RS,T
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REAL (WP), INTENT(OUT) :: DT,DT2
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!
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REAL (WP) :: EC,D_EC_1,D_EC_2
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REAL (WP) :: EF
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REAL (WP) :: D1(3:6),D2(3:6),D3(3:6)
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REAL (WP) :: U,U3,U4,U5,U6
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!
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REAL (WP) :: SQRT
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!
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DATA D1 / 0.093623E0_WP, 0.194288E0_WP, 0.051445E0_WP, 0.005449E0_WP / ! RPA
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DATA D2 / 0.126362E0_WP, 0.001428E0_WP, 0.014278E0_WP, -0.004522E0_WP / ! GW
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DATA D3 / 0.271191E0_WP, -0.009998E0_WP, -0.036383E0_WP, 0.006706E0_WP / ! GZ
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!
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U = SQRT(RS) !
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U3 = U * U * U !
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U4 = U3 * U !
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U5 = U4 * U !
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U6 = U5 * U !
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!
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! Correlation energy and its derivatives
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!
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EC = EC_3D(EC_TYPE,1,RS,T) !
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CALL DERIVE_EC_3D(EC_TYPE,1,5,RS,T,D_EC_1,D_EC_2) !
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!
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! E_F in Rydberg
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!
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EF = TWO * EF_AU ! EF_AU in Hartree
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!
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DT = - FIVE * THIRD * (EC + RS * D_EC_1) / EF !
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!
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! Parametrization of delta_t2
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!
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IF(I_DE == 1) THEN !
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DT2 = D1(3) * U3 + D1(4) * U4 + D1(5) * U5 + D1(6) * U6 !
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ELSE IF(I_DE == 2) THEN !
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DT2 = D2(3) * U3 + D2(4) * U4 + D2(5) * U5 + D2(6) * U6 ! ref. (1) eq. (B1)
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ELSE IF(I_DE == 3) THEN !
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DT2 = D3(3) * U3 + D3(4) * U4 + D3(5) * U5 + D3(6) * U6 !
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END IF !
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!
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END SUBROUTINE DELTA_KIN_3D
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!
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END MODULE DELTA_KIN
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