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mc_hs_module.f90
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mc_hs_module.f90
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! mc_hs_module.f90
! Overlap routines for MC simulation, hard spheres
MODULE mc_module
!------------------------------------------------------------------------------------------------!
! This software was written in 2016/17 !
! by Michael P. Allen <[email protected]>/<[email protected]> !
! and Dominic J. Tildesley <[email protected]> ("the authors"), !
! to accompany the book "Computer Simulation of Liquids", second edition, 2017 ("the text"), !
! published by Oxford University Press ("the publishers"). !
! !
! LICENCE !
! Creative Commons CC0 Public Domain Dedication. !
! To the extent possible under law, the authors have dedicated all copyright and related !
! and neighboring rights to this software to the PUBLIC domain worldwide. !
! This software is distributed without any warranty. !
! You should have received a copy of the CC0 Public Domain Dedication along with this software. !
! If not, see <http://creativecommons.org/publicdomain/zero/1.0/>. !
! !
! DISCLAIMER !
! The authors and publishers make no warranties about the software, and disclaim liability !
! for all uses of the software, to the fullest extent permitted by applicable law. !
! The authors and publishers do not recommend use of this software for any purpose. !
! It is made freely available, solely to clarify points made in the text. When using or citing !
! the software, you should not imply endorsement by the authors or publishers. !
!------------------------------------------------------------------------------------------------!
USE, INTRINSIC :: iso_fortran_env, ONLY : output_unit, error_unit
IMPLICIT NONE
PRIVATE
! Public routines
PUBLIC :: introduction, conclusion, allocate_arrays, deallocate_arrays
PUBLIC :: overlap_1, overlap, n_overlap
! Public data
INTEGER, PUBLIC :: n ! Number of atoms
REAL, DIMENSION(:,:), ALLOCATABLE, PUBLIC :: r ! Positions (3,n)
! Private data
INTEGER, PARAMETER :: lt = -1, gt = 1 ! j-range options
CONTAINS
SUBROUTINE introduction
IMPLICIT NONE
WRITE ( unit=output_unit, fmt='(a)' ) 'Hard sphere potential'
WRITE ( unit=output_unit, fmt='(a)' ) 'Diameter, sigma = 1'
WRITE ( unit=output_unit, fmt='(a)' ) 'Energy, kT = 1'
END SUBROUTINE introduction
SUBROUTINE conclusion
IMPLICIT NONE
WRITE ( unit=output_unit, fmt='(a)') 'Program ends'
END SUBROUTINE conclusion
SUBROUTINE allocate_arrays
IMPLICIT NONE
ALLOCATE ( r(3,n) )
END SUBROUTINE allocate_arrays
SUBROUTINE deallocate_arrays
IMPLICIT NONE
DEALLOCATE ( r )
END SUBROUTINE deallocate_arrays
FUNCTION overlap ( box )
IMPLICIT NONE
LOGICAL :: overlap ! Shows if an overlap was detected
REAL, INTENT(in) :: box ! Simulation box length
! Actual calculation is performed by function overlap_1
INTEGER :: i
IF ( n > SIZE(r,dim=2) ) THEN ! should never happen
WRITE ( unit=error_unit, fmt='(a,2i15)' ) 'Array bounds error for r', n, SIZE(r,dim=2)
STOP 'Error in overlap'
END IF
DO i = 1, n - 1
IF ( overlap_1 ( r(:,i), i, box, gt ) ) THEN
overlap = .TRUE. ! Overlap detected
RETURN ! Return immediately
END IF
END DO
overlap = .FALSE. ! No overlaps detected
END FUNCTION overlap
FUNCTION overlap_1 ( ri, i, box, j_range ) RESULT ( overlap )
IMPLICIT NONE
LOGICAL :: overlap ! Shows if an overlap was detected
REAL, DIMENSION(3), INTENT(in) :: ri ! Coordinates of atom of interest
INTEGER, INTENT(in) :: i ! Index of atom of interest
REAL, INTENT(in) :: box ! Simulation box length
INTEGER, OPTIONAL, INTENT(in) :: j_range ! Optional partner index range
! Detects overlap of atom in ri
! The coordinates in ri are not necessarily identical with those in r(:,i)
! The optional argument j_range restricts partner indices to j>i, or j<i
! It is assumed that r is in units where box = 1
INTEGER :: j, j1, j2
REAL :: box_sq, rij_sq
REAL, DIMENSION(3) :: rij
IF ( n > SIZE(r,dim=2) ) THEN ! should never happen
WRITE ( unit=error_unit, fmt='(a,2i15)' ) 'Array bounds error for r', n, SIZE(r,dim=2)
STOP 'Error in overlap_1'
END IF
IF ( PRESENT ( j_range ) ) THEN
SELECT CASE ( j_range )
CASE ( lt ) ! j < i
j1 = 1
j2 = i-1
CASE ( gt ) ! j > i
j1 = i+1
j2 = n
CASE default ! should never happen
WRITE ( unit = error_unit, fmt='(a,i10)') 'j_range error ', j_range
STOP 'Impossible error in overlap_1'
END SELECT
ELSE
j1 = 1
j2 = n
END IF
box_sq = box**2
DO j = j1, j2 ! Loop over selected range of partners
IF ( i == j ) CYCLE ! Skip self
rij(:) = ri(:) - r(:,j)
rij(:) = rij(:) - ANINT ( rij(:) ) ! periodic boundaries in box=1 units
rij_sq = SUM ( rij**2 )
rij_sq = rij_sq * box_sq ! now in sigma=1 units
IF ( rij_sq < 1.0 ) THEN
overlap = .TRUE. ! Overlap detected
RETURN ! Return immediately
END IF
END DO ! End loop over selected range of partners
overlap = .FALSE. ! No overlaps detected
END FUNCTION overlap_1
FUNCTION n_overlap ( box )
IMPLICIT NONE
INTEGER :: n_overlap ! Counts overlaps
REAL, INTENT(in) :: box ! Simulation box length
! This routine is used in the calculation of pressure
! Actual calculation is performed by function n_overlap_1
INTEGER :: i
IF ( n > SIZE(r,dim=2) ) THEN ! should never happen
WRITE ( unit=error_unit, fmt='(a,2i15)' ) 'Array bounds error for r', n, SIZE(r,dim=2)
STOP 'Error in n_overlap'
END IF
n_overlap = 0
DO i = 1, n - 1
n_overlap = n_overlap + n_overlap_1 ( r(:,i), i, box, gt )
END DO
END FUNCTION n_overlap
FUNCTION n_overlap_1 ( ri, i, box, j_range ) RESULT ( n_overlap )
IMPLICIT NONE
INTEGER :: n_overlap ! Counts overlaps
REAL, DIMENSION(3), INTENT(in) :: ri ! Coordinates of atom of interest
INTEGER, INTENT(in) :: i ! Index of atom of interest
REAL, INTENT(in) :: box ! Simulation box length
INTEGER, OPTIONAL, INTENT(in) :: j_range ! Optional partner index range
! Counts overlaps of atom in ri
! The coordinates in ri are not necessarily identical with those in r(:,i)
! The optional argument j_range restricts partner indices to j>i, or j<i
! It is assumed that r is in units where box = 1
! This routine is used in the calculation of pressure
INTEGER :: j, j1, j2
REAL :: box_sq, rij_sq
REAL, DIMENSION(3) :: rij
IF ( n > SIZE(r,dim=2) ) THEN ! should never happen
WRITE ( unit=error_unit, fmt='(a,2i15)' ) 'Array bounds error for r', n, SIZE(r,dim=2)
STOP 'Error in n_overlap_1'
END IF
IF ( PRESENT ( j_range ) ) THEN
SELECT CASE ( j_range )
CASE ( lt ) ! j < i
j1 = 1
j2 = i-1
CASE ( gt ) ! j > i
j1 = i+1
j2 = n
CASE default ! should never happen
WRITE ( unit = error_unit, fmt='(a,i10)') 'j_range error ', j_range
STOP 'Impossible error in n_overlap_1'
END SELECT
ELSE
j1 = 1
j2 = n
END IF
box_sq = box**2
n_overlap = 0
DO j = j1, j2
IF ( i == j ) CYCLE ! Skip self
rij(:) = ri(:) - r(:,j)
rij(:) = rij(:) - ANINT ( rij(:) ) ! Periodic boundaries in box=1 units
rij_sq = SUM ( rij**2 )
rij_sq = rij_sq * box_sq ! Now in sigma=1 units
IF ( rij_sq < 1.0 ) n_overlap = n_overlap + 1
END DO
END FUNCTION n_overlap_1
END MODULE mc_module