File: sdelta_fd.f90

package info (click to toggle)
elkcode 5.4.24-2
  • links: PTS, VCS
  • area: main
  • in suites: buster, sid
  • size: 12,840 kB
  • sloc: f90: 48,415; fortran: 22,457; perl: 965; makefile: 384; sh: 369; python: 105; ansic: 67
file content (34 lines) | stat: -rw-r--r-- 744 bytes parent folder | download
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34

! Copyright (C) 2002-2005 J. K. Dewhurst, S. Sharma and C. Ambrosch-Draxl.
! This file is distributed under the terms of the GNU Lesser General Public
! License. See the file COPYING for license details.

!BOP
! !ROUTINE: sdelta_fd
! !INTERFACE:
real(8) function sdelta_fd(x)
! !INPUT/OUTPUT PARAMETERS:
!   x : real argument (in,real)
! !DESCRIPTION:
!   Returns the Fermi-Dirac approximation to the Dirac delta function
!   $$ \tilde\delta(x)=\frac{e^{-x}}{(1+e^{-x})^2}. $$
!
! !REVISION HISTORY:
!   Created April 2003 (JKD)
!EOP
!BOC
implicit none
! arguments
real(8), intent(in) :: x
! local variables
real(8) t1
if (abs(x).gt.50.d0) then
  sdelta_fd=0.d0
  return
end if
t1=exp(-x)
sdelta_fd=t1/((1.d0+t1)**2)
return
end function
!EOC