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C Copyright (c) 2003-2010 University of Florida
C
C This program is free software; you can redistribute it and/or modify
C it under the terms of the GNU General Public License as published by
C the Free Software Foundation; either version 2 of the License, or
C (at your option) any later version.
C This program is distributed in the hope that it will be useful,
C but WITHOUT ANY WARRANTY; without even the implied warranty of
C MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the
C GNU General Public License for more details.
C The GNU General Public License is included in this distribution
C in the file COPYRIGHT.
SUBROUTINE NLO__OPTIMUM_ATOM_INDEX_ORDER
+
+ ( NATOM,N2CEN,
+ INDEX,
+ AT2CEN,
+
+ ATORD )
+
C------------------------------------------------------------------------
C OPERATION : NLO__OPTIMUM_ATOM_INDEX_ORDER
C MODULE : Natural Localized Orbitals
C MODULE-ID : NLO
C DESCRIPTION : Given a set of ordered atomic pair (2 center) indices,
C this routine extracts an optimum atomic index sequence
C via the following algorithm:
C
C 1) Take first index pair I,J and start the
C atomic index sequence with I.
C
C 2) Go through the index pair list from the
C beginning to the end, adding all atomic
C indices {K} in that order, that contain
C atom I in all index pairs {I,K}.
C
C 3) Take second element I of already established
C partial atomic index sequence and repeat
C step 2). Then take third element I, etc...
C
C Observe, that isolated sequences of atoms (i.e. not
C bonded) might occur in cases the program deals
C with a molecule composed of well separated fragments.
C Also if the set of all index pairs does not contain
C all atom indices, the atomic index sequence will be
C completed by those missing.
C
C A special case arises, if no index pairs were found
C from the bond order matrix. This indicates a isolated
C atom or a set of well separated atoms. In both these
C cases we have N2CEN = 0 and no info is sitting in
C array AT2CEN. Thus the case N2CEN = 0 has to be dealt
C with separately.
C
C Input:
C
C NATOM = total # of atoms
C N2CEN = # of ordered atomic index pairs
C that will be considered for
C optimum atomic index sequence
C construction.
C INDEX = will hold info about used atoms
C AT2CEN (1,N) = 1st atomic index of N-th ordered
C pair.
C AT2CEN (2,N) = 2nd atomic index of N-th ordered
C pair.
C
C
C Output:
C
C ATORD (I) = I-th atomic index in sequence.
C
C
C AUTHOR : Norbert Flocke
C------------------------------------------------------------------------
C
C
C ...include files and declare variables.
C
C
IMPLICIT NONE
LOGICAL CASE1,CASE2
LOGICAL CHECK
LOGICAL IGNORE
INTEGER AT1,AT2
INTEGER ATNEW
INTEGER ATOM
INTEGER I,J,M
INTEGER IDX
INTEGER N2CEN
INTEGER NATOM
INTEGER USED,NOTUSED
INTEGER ATORD (1:NATOM)
INTEGER INDEX (1:NATOM)
INTEGER AT2CEN (1:2,1:N2CEN)
C
C
C------------------------------------------------------------------------
C
C
C ...handle special case of isolated atom(s) only.
C This requires straightforward consecutive indexing.
C
C
IF (N2CEN.EQ.0) THEN
DO ATOM = 1,NATOM
ATORD (ATOM) = ATOM
END DO
RETURN
END IF
C
C
C ...initialize used atoms index array.
C
C
USED = 1
NOTUSED = 0
DO ATOM = 1,NATOM
INDEX (ATOM) = NOTUSED
END DO
C
C
C ...initialize atom index list.
C
C
M = 1
IDX = 1
ATOM = AT2CEN (1,1)
ATORD (1) = ATOM
INDEX (ATOM) = USED
C
C
C ...check presence of atom ATOM in the set of ordered
C index pairs and add the new atoms to the atom index
C list.
C
C
1000 DO I = 1,N2CEN
AT1 = AT2CEN (1,I)
AT2 = AT2CEN (2,I)
CASE1 = AT1 .EQ. ATOM
CASE2 = AT2 .EQ. ATOM
CHECK = CASE1 .OR. CASE2
IF (CHECK) THEN
IF (CASE1) THEN
ATNEW = AT2
ELSE
ATNEW = AT1
END IF
IGNORE = .FALSE.
DO J = 1,M
IGNORE = IGNORE .OR. (ATORD (J).EQ.ATNEW)
END DO
IF (.NOT.IGNORE) THEN
M = M + 1
ATORD (M) = ATNEW
INDEX (ATNEW) = USED
END IF
END IF
END DO
IDX = IDX + 1
IF (IDX.LE.M) THEN
C
C
C ...more atoms are present in current atom index list
C ready for checking. Pick the next in line and go
C back.
C
C
ATOM = ATORD (IDX)
GOTO 1000
ELSE
C
C
C ...all atoms in current atom index list have been
C checked. Check next, if still atoms need to be
C added to this list corresponding to untreated
C index pairs. If so, take next available atom and
C go back to the checking procedure.
C
C
DO I = 1,N2CEN
AT1 = AT2CEN (1,I)
AT2 = AT2CEN (2,I)
CASE1 = INDEX (AT1) .EQ. NOTUSED
CASE2 = INDEX (AT2) .EQ. NOTUSED
CHECK = CASE1 .OR. CASE2
IF (CHECK) THEN
IF (CASE1) THEN
ATOM = AT1
ELSE
ATOM = AT2
END IF
M = IDX
ATORD (IDX) = ATOM
INDEX (ATOM) = USED
GOTO 1000
END IF
END DO
C
C
C ...we get here if all atoms of all index pairs
C have been ordered. There might be still atoms
C which are not bonded to any of the rest and
C which still must be added to the atom index list
C in order to complete it.
C
C
DO ATOM = 1,NATOM
IF (INDEX (ATOM).EQ.NOTUSED) THEN
M = M + 1
ATORD (M) = ATOM
END IF
END DO
END IF
C
C
C ...ready!
C
C
RETURN
END
|
