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allen-tildesley-book
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README,
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f.01,
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older-version
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********************************************************************************
** FICHE F.14. ALGORITHM TO HANDLE INDICES IN CONSTANT MU VT MONTE CARLO **
** This FORTRAN code is intended to illustrate points made in the text. **
** To our knowledge it works correctly. However it is the responsibility of **
** the user to test it, if it is to be used in a research application. **
********************************************************************************
C *******************************************************************
C ** INDEX-HANDLING IN GRAND CANONICAL MONTE CARLO SIMULATION. **
C ** **
C ** ROUTINES SUPPLIED: **
C ** **
C ** SUBROUTINE ADD ( RXNEW, RYNEW, RZNEW, N ) **
C ** ADDS AN ATOM TO THE ARRAY LOCATE. **
C ** SUBROUTINE REMOVE ( NLOC, IPULL, N ) **
C ** REMOVES AN ATOM FROM THE ARRAY LOCATE. **
C ** **
C ** PRINCIPAL VARIABLES: **
C ** **
C ** INTEGER N NUMBER OF ATOMS BEFORE TRIAL **
C ** INTEGER NMAX MAXIMUM NUMBER OF ATOMS **
C ** INTEGER IPULL INDEX OF ATOM FOR REMOVAL **
C ** INTEGER NLOC POSITION OF N IN LOCATE **
C ** INTEGER NTRIAL NUMBER OF ATOMS DURING TRIAL **
C ** INTEGER LOCATE(NMAX) ARRAY OF ACTIVE ATOM INDICES **
C ** REAL RXNEW,RYNEW,RZNEW POSITION FOR ADDITION OF AN ATOM **
C ** REAL RX(NMAX), ETC. POSITIONS OF ATOMS **
C ** **
C ** USAGE: **
C ** **
C ** ROUTINE ADD IS CALLED AFTER A SUCCESSFUL TRIAL ADDITION. **
C ** ROUTINE REMOVE IS CALLED AFTER A SUCCESSFUL TRIAL REMOVAL. **
C ** THE ARRAY LOCATE IS UPDATED IN EACH CASE. **
C *******************************************************************
SUBROUTINE ADD ( RXNEW, RYNEW, RZNEW, N )
COMMON / BLOCK1 / RX, RY, RZ
COMMON / BLOCK2 / LOCATE
C *******************************************************************
C ** SUBROUTINE TO ADD AN ATOM TO THE ARRAY LOCATE. **
C ** **
C ** THERE ARE N ATOMS IN THE SIMULATION BEFORE THE NEW ADDITION **
C *******************************************************************
INTEGER NMAX
PARAMETER ( NMAX = 500 )
REAL RX(NMAX), RY(NMAX), RZ(NMAX)
INTEGER LOCATE(NMAX)
REAL RXNEW, RYNEW, RZNEW
INTEGER N, IPULL
INTEGER INEW, NTRIAL
C *******************************************************************
NTRIAL = N + 1
INEW = LOCATE(NTRIAL)
IF ( INEW .EQ. 0 ) THEN
C ** ATOM REQUIRES A NEW NUMBER **
LOCATE(NTRIAL) = NTRIAL
INEW = NTRIAL
ENDIF
C ** FIT NEW ATOM INTO THE ARRAY **
RX(INEW) = RXNEW
RY(INEW) = RYNEW
RZ(INEW) = RZNEW
RETURN
END
SUBROUTINE REMOVE ( NLOC, IPULL, N )
COMMON / BLOCK1 / RX, RY, RZ
COMMON / BLOCK2 / LOCATE
C *******************************************************************
C ** SUBROUTINE TO REMOVE AN ATOM FROM THE ARRAY LOCATE. **
C ** **
C ** THERE ARE N ATOMS IN THE SIMULATION BEFORE THE REMOVAL. **
C ** ELEMENT IPULL OF LOCATE IS TO BE DESTROYED. **
C *******************************************************************
INTEGER NMAX
PARAMETER ( NMAX = 500 )
REAL RX(NMAX), RY(NMAX), RZ(NMAX)
INTEGER LOCATE(NMAX)
INTEGER N, IPULL, NLOC
INTEGER K
C *******************************************************************
IF ( NLOC .LT. N ) THEN
C ** CLOSE UP THE ARRAY LOCATE AFTER THE REMOVAL **
DO 10 K = NLOC + 1, N
LOCATE(K - 1) = LOCATE(K)
10 CONTINUE
C ** PLACE THE GHOST ATOM IPULL JUST OUTSIDE THE ACTIVE **
C ** RANGE OF THE ARRAY LOCATE FOR FUTURE USE **
LOCATE(N) = IPULL
ENDIF
RETURN
END
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