114 lines
3.8 KiB
Fortran
114 lines
3.8 KiB
Fortran
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!=======================================================================
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MODULE COULOMB_K
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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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!=======================================================================
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!
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SUBROUTINE COULOMB_FF(DMN,UNIT,Q,KS,V_C)
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!
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! This subroutine computes Coulomb potentials in the k-space
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! in all dimensions, including the form factors
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! to account for various confinements
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!
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!
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! Input parameters:
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!
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! * DMN : dimension of the system
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! * UNIT : system unit
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! * Q : wave vector in UNIT
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! * KS : screening wave vector in UNIT
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!
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!
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! Output variables :
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!
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! * V_C : Coulomb potential in k-space (in UNIT)
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!
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!
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!
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! Note: In the coding of the different form factors,
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! we have taken the following convention:
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!
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! 3D : V(q) = e^2 / (EPS_0 * q^2) * FF [SI]
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! 4 pi e^2 / q^2 * FF [CGS]
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!
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! Q2D,2D : V(q) = e^2 / (2*EPS_0 * q) * FF [SI]
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! 2 pi e^2 / q * FF [CGS]
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!
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! Q1D,1D : V(q) = e^2 / EPS_0 * FF [SI]
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! 4 pi e^2 * FF [CGS]
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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 : 5 Oct 2020
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!
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!
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USE REAL_NUMBERS, ONLY : FOUR,HALF
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USE PI_ETC, ONLY : PI
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USE CONFIN_VAL, ONLY : R0
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USE CONFINEMENT_FF, ONLY : CONFIN_FF
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USE CONSTANTS_P1, ONLY : E,EPS_0
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USE FERMI_SI, ONLY : KF_SI
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USE FERMI_AU, ONLY : KF_AU
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!
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IMPLICIT NONE
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!
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CHARACTER (LEN = 3) :: UNIT
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CHARACTER (LEN = 2) :: DMN
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!
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REAL (WP) :: Q,KS
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REAL (WP) :: V_C
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REAL (WP) :: X,COEF,Q2,KS2,QKS2
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REAL (WP) :: FF
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!
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REAL (WP) :: SQRT
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!
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! Unit-dependent factors
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!
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IF(UNIT == 'SIU') THEN !
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COEF = E * E / EPS_0 !
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X = HALF * Q / KF_SI ! X = q / (2 * k_F)
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ELSE IF(UNIT == 'CGS') THEN !
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COEF = FOUR * PI * E * E !
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X = HALF * Q / KF_AU ! X = q / (2 * k_F)
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END IF !
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!
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Q2 = Q * Q !
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KS2 = KS * KS !
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QKS2 = Q2 + KS2 !
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!
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IF(DMN == '3D') THEN !
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!
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V_C = COEF / QKS2 !
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!
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ELSE IF(DMN == '2D') THEN !
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!
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FF = CONFIN_FF(X) !
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V_C = HALF * COEF * FF / SQRT(QKS2) !
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!
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ELSE IF(DMN == 'Q2') THEN !
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!
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FF = CONFIN_FF(X) !
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V_C = HALF * COEF * FF / SQRT(QKS2) !
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!
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ELSE IF(DMN == 'Q1') THEN !
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!
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FF = CONFIN_FF(X) !
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V_C = COEF * FF !
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!
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ELSE IF(DMN == '1D') THEN !
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!
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FF = CONFIN_FF(X) !
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V_C = COEF * FF !
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!
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END IF !
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!
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END SUBROUTINE COULOMB_FF
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!
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END MODULE COULOMB_K
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