99 lines
2.5 KiB
Fortran
99 lines
2.5 KiB
Fortran
!
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!=======================================================================
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!
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MODULE ELECTRON_PHONON_INT
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!
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USE ACCURACY_REAL
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!
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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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!
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SUBROUTINE EL_PHONON_INT_3D(X,EPH,EPS0,EPSI,IP)
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!
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! This subroutine computes the electron-phonon interaction
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! for 3D systems
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!
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!
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! Input parameters:
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!
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! * X : dimensionless factor --> X = q / (2 * k_F)
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! * EPH : phonon energy -SI)
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! * EPS0 :
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! * EPSI :
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! * IP_TYPE : type of electron-phonon interaction
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! IP_TYPE = 'DEHI' --> Degani-Hipolito approximation
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!
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! Output parameters:
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!
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! * IP : electron-phonon interaction
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!
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! Author : D. Sébilleau
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!
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! Last modified : 11 Jun 2020
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!
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IMPLICIT NONE
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!
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CHARACTER (LEN = 4) :: IP_TYPE
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!
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REAL (WP), INTENT(IN) :: X,EPH,EPS0,EPSI
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!
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COMPLEX (WP) :: IP
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!
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IF(IP_TYPE == 'DEHI') THEN !
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IP = DEHI_EP_3D(X,EPH,EPS0,EPSI) !
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END IF !
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!
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END SUBROUTINE EL_PHONON_INT_3D
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!
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!=======================================================================
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!
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FUNCTION DEHI_EP_3D(X,EPH,EPS0,EPSI)
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!
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! This function computes the Fourier coefficient of the electron-phonon
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! interaction
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!
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! Reference: (1) M. H. Degani and O. Hipolito, Phys. Rev. B 35, 9345-9348 (1987)
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!
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!
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! Input parameters:
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!
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! * X : dimensionless factor --> X = q / (2 * k_F)
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! * EPH : phonon energy -SI)
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! * EPS0 :
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! * EPSI :
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!
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! Output parameters:
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!
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! * DEHI_EPI : Fourier coefficient
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!
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! Author : D. Sébilleau
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!
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! Last modified : 11 Jun 2020
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!
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!
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USE REAL_NUMBERS, ONLY : ONE,TWO
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USE COMPLEX_NUMBERS, ONLY : IC
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USE CONSTANTS_P1, ONLY : E
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USE FERMI_SI, ONLY : KF_SI
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USE PI_ETC, ONLY : PI
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!
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!
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REAL (WP), INTENT(IN) :: X,EPH,EPS0,EPSI
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REAL (WP) :: Q,SQR
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!
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REAL (WP) :: SQRT
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!
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COMPLEX (WP) :: DEHI_EP_3D
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!
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Q = TWO * X * KF_SI ! phonon momentum
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SQR = SQRT(TWO * PI * E * E * (ONE / EPSI - ONE / EPS0) /EPH) !
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!
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DEHI_EP_3D = - IC * EPH * SQR / Q ! ref. 1 eq. (2)
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!
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END FUNCTION DEHI_EP_3D
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!
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END MODULE ELECTRON_PHONON_INT
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