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