65 lines
1.4 KiB
Fortran
65 lines
1.4 KiB
Fortran
!
|
|
!=======================================================================
|
|
!
|
|
MODULE SQ_I
|
|
!
|
|
USE ACCURACY_REAL
|
|
!
|
|
! It contains the following functions/subroutines:
|
|
!
|
|
! * FUNCTION SQ_I_3D(X,GR0_MODE)
|
|
!
|
|
CONTAINS
|
|
!
|
|
!
|
|
!=======================================================================
|
|
!
|
|
FUNCTION SQ_I_3D(X,RS,GR0_MODE)
|
|
!
|
|
! This function computes the asymptotic behaviour of the static
|
|
! structure factor at infinity:
|
|
!
|
|
! lim (q --> infinity) S(q)
|
|
!
|
|
! References: (1) N. Iwamoto, E. Krotscheck and D. Pines,
|
|
! Phys. Rev. B 28, 3936-3951 (1984)
|
|
!
|
|
!
|
|
! Input parameters:
|
|
!
|
|
! * X : dimensionless factor --> X = q / (2 * k_F)
|
|
! * RS : Wigner-Seitz radius (in units of a_0)
|
|
! * GR0_MODE : g(0) (3D)
|
|
!
|
|
!
|
|
!
|
|
! Author : D. Sébilleau
|
|
!
|
|
! Last modified : 5 Aug 2020
|
|
!
|
|
!
|
|
USE REAL_NUMBERS, ONLY : ONE,SIX
|
|
USE CONSTANTS_P1, ONLY : BOHR
|
|
USE FERMI_SI, ONLY : KF_SI
|
|
USE PI_ETC, ONLY : PI
|
|
USE GR_0, ONLY : GR_0_3D
|
|
!
|
|
IMPLICIT NONE
|
|
!
|
|
CHARACTER (LEN = 4) :: GR0_MODE
|
|
!
|
|
REAL (WP), INTENT(IN) :: X,RS
|
|
REAL (WP) :: SQ_I_3D
|
|
REAL (WP) :: COEF
|
|
!
|
|
COEF = ONE / (SIX * PI * BOHR * KF_SI) !
|
|
!
|
|
SQ_I_3D = ONE - COEF * GR_0_3D(RS,GR0_MODE) / (X * X * X * X) !
|
|
!
|
|
RETURN
|
|
!
|
|
END
|
|
!
|
|
END MODULE SQ_I
|
|
|