C     Last change:  ALI  18 May 2007   10:41 am
C
C  ==========================================================================
C  ==========================================================================
C
C  DDDDDDD   IIII   CCCCCC   VV    VV   OOOOOO   LL          0000        66
C  DD    DD   II   CC    CC  VV    VV  OO    OO  LL         00  00      66
C  DD    DD   II   CC        VV    VV  OO    OO  LL        00    00    66
C  DD    DD   II   CC        VV    VV  OO    OO  LL        00    00   66  66
C  DD    DD   II   CC         VV  VV   OO    OO  LL        00    00   66   66
C  DD    DD   II   CC    CC    VVVV    OO    OO  LL    LL   00  00    66   66
C  DDDDDDD   IIII   CCCCCC      VV      OOOOOO   LLLLLLLL    0000      66666
C
C  ==========================================================================
C  ==========================================================================
C
C     TWO OPTIONS ARE AVAILABLE WITH DICVOL06
C     ---------------------------------------
C
C >> OPTION 0 IS DICVOL04 (OPTIMISED SEARCH TO BE USED WITH NORMAL QUALITY
C    DATA)
C
C >> OPTION 1 OFFERS AN EXTENDED (EXHAUSTIVE) SEARCH (FOR DIFFICULT CASES)
C
C  [COMPARED TO DICVOL04 (2004) ONLY ONE ADDITIONAL INPUT PARAMETER IS ADDED
C  IN DICVOL06, i.e. OPTION IN CARD 5 (SEE BELOW)]
C
C        --------------------------------------------------------------
C        --------------------------------------------------------------
C        --------------------------------------------------------------
C        |    TO EXECUTE THE PROGRAM, ENTER :      DICVOL06           | 
C        |                                                            |
C        |    THEN, ENTER THE INPUT FILE NAME and OUTPUT FILE NAME    |
C        --------------------------------------------------------------
C        --------------------------------------------------------------
C        --------------------------------------------------------------
C
C     PROGRAM FOR THE AUTOMATIC INDEXING OF POWDER DIFFRACTION PATTERNS BY
C     THE SUCCESSIVE DICHOTOMY METHOD.
C
C     ------------------------------------------------------------------
C >>>>    THE REFERENCE FOR THIS PROGRAM, TO REPORT IN PUBLICATIONS, IS:
C
C >>>>    (1): A. Boultif & D. Louer, J. Appl. Cryst. 37, 724-731, 2004
C     ------------------------------------------------------------------
C
C     THE FOLLOWING CRYSTAL SYSTEMS CAN BE ANALYZED: CUBIC, TETRAGONAL,
C     HEXAGONAL, ORTHORHOMBIC, MONOCLINIC AND TRICLINIC.
C
C     PRECURSOR PROGRAMS:
C     P1 & P2 (REF. 2), DICVOL (REF. 3), DICVOL91 (REF. 4), DICVOL04 (REF. 1)
C
C                                  =======================
C
C     FOR FURTHER INFORMATION CONTACT
C               D. LOUER
C               E-MAIL  Daniel.Louer@free.fr
C
C         OR
C               A. BOULTIF
C               LABORATOIRE DE CRISTALLOGRAPHIE
C               DEPARTEMENT DE PHYSIQUE
C               FACULTE DES SCIENCES EXACTES
C               UNIVERSITE MENTOURI - CONSTANTINE
c               25000 CONSTANTINE - ALGERIE
C               TEL./FAX  (213) 31 61 47 47
C               E-MAIL  ABoultif@ifrance.com
C
C      ---------------------------------------------------------------
C      |            G E N E R A L   I N S T R U C T I O N S          |
C      ---------------------------------------------------------------
C
C      DICVOL PROPOSES SOLUTIONS; THE USER DISPOSES OF THEM.
C      THE AUTHORS DISCLAIM RESPONSABILITY FOR ALL USE OF THIS PROGRAM
C      ---------------------------------------------------------------
C
C ===> BEFORE USING DICVOL06, PLEASE READ REFERENCE 1, AS WELL AS THE
C ===> INSTRUCTIONS AND RECOMMENDATIONS BELOW.
C
C      _______________
C      INPUT DATA FILE
C      ---------------
C
C  CARD 1  TITLE                                          FREE FORMAT
C
C
C  CARD 2  N,ITYPE,JC,JT,JH,JO,JM,JTR                     FREE FORMAT
C
C          N               NUMBER OF LINES USED FOR SEARCHING SOLUTIONS.
C                          (This number is, generally, lower than the
C                          number N_TOTAL of input lines). e.g. N = 20.
C          ITYPE           SPACING DATA TYPE.
C                      =1  THETA BRAGG ANGLE IN DEGREES.
C                      =2  2-THETA ANGLE IN DEGREES.
C                      =3  D-SPACING IN ANGSTROM UNIT.
C                      =4  Q SPECIFIED IN Q-UNITS AS E+04/D**2.
C          JC          =0  CUBIC SYSTEM IS NOT TESTED.
C                      =1  CUBIC SYSTEM IS TESTED.
C          JT          =0  TETRAGONAL SYSTEM IS NOT TESTED.
C                      =1  TETRAGONAL SYSTEM IS TESTED.
C          JH          =0  HEXAGONAL SYSTEM IS NOT TESTED.
C                      =1  HEXAGONAL SYSTEM IS TESTED.
C          JO          =0  ORTHORHOMBIC SYSTEM IS NOT TESTED.
C                      =1  ORTHORHOMBIC SYSTEM IS TESTED.
C          JM          =0  MONOCLINIC SYSTEM IS NOT TESTED.
C                      =1  MONOCLINIC SYSTEM IS TESTED.
C          JTR         =0  TRICLINIC SYSTEM IS NOT TESTED.
C                      =1  TRICLINIC SYSTEM IS TESTED.
C
C
C  CARD 3  AMAX,BMAX,CMAX,VOLMIN,VOLMAX,BEMIN,BEMAX       FREE FORMAT
C
C          AMAX    MAXIMUM VALUE OF UNIT CELL DIMENSION A, IN ANGSTROMS.
C                  (IF AMAX= 0.0 DEFAULT= 25. ANGSTROMS)
C          BMAX    MAXIMUM VALUE OF UNIT CELL DIMENSION B, IN ANGSTROMS.
C                  (IF BMAX= 0.0 DEFAULT= 25. ANGSTROMS)
C          CMAX    MAXIMUM VALUE OF UNIT CELL DIMENSION C, IN ANGSTROMS.
C                  (IF CMAX= 0.0 DEFAULT= 25. ANGSTROMS)
C          VOLMIN  MINIMUM VOLUME FOR UNIT CELLS IN ANGSTROMS**3.
C          VOLMAX  MAXIMUM VOLUME FOR UNIT CELLS IN ANGSTROMS**3.
C                  (IF VOLMAX= 0.0 DEFAULT= 2500. ANGSTROMS**3)
C          BEMIN   MINIMUM BETA ANGLE FOR MONOCLINIC CELLS IN DEGREES
C                  (IF BEMIN= 0.0 DEFAULT= 90. DEGREES).
C          BEMAX   MAXIMUM BETA ANGLE FOR MONOCLINIC CELLS IN DEGREES
C                  (IF BEMAX= 0.0 DEFAULT= 125. DEGREES).
C
C
C  CARD 4  WAVE,POIMOL,DENS,DELDEN                        FREE FORMAT
C
C          WAVE    WAVELENGTH IN ANGSTROMS (DEFAULT=0.0 IF CU K ALPHA1).
C          POIMOL  MOLECULAR WEIGHT OF ONE FORMULA UNIT IN A.M.U.
C                  (DEFAULT =0.0 IF FORMULA WEIGHT NOT KNOWN).
C          DENS    MEASURED DENSITY IN G CM(**-3)
C                  (DEFAULT =0.0 IF DENSITY NOT KNOWN).
C          DELDEN  ABSOLUTE ERROR IN MEASURED DENSITY.
C                  (DEFAULT =0.0 IF DENSITY NOT KNOWN).
C
C
C  CARD 5  EPS,FOM,N_IMP,ZERO_S,ZERO_REF,OPTION           FREE FORMAT
C
C          EPS       =0.0  THE ABSOLUTE ERROR ON EACH OBSERVED LINE
C                          IS TAKEN TO 0.03 DEG. 2THETA (DEFAULT VALUE)
C                          WHATEVER THE SPACING DATA TYPE (ITYPE IN CARD 2).
C                    =1.0  THE ABSOLUTE ERROR ON EACH OBSERVED LINE IS
C                          INPUT INDIVIDUALLY FROM CARD 6, AFTER THE
C                          OBSERVED 'D(I)' ON THE SAME LINE, ACCORDING
C                          TO THE SPACING DATA UNIT (e.g.  18.678 0.018 in
C                          deg. 2theta)
C                    EPS NE 0.0 AND 1.0
C                          THE ABSOLUTE ERROR IS TAKEN AS A CONSTANT
C                          (= EPS),IN DEG. 2THETA, WHATEVER THE SPACING
C                          DATA TYPE (ITYPE IN CARD 2) (e.g. 0.02, which will
C                          apply to all input lines).
C          FOM             LOWER FIGURE OF MERIT M(N) REQUIRED FOR PRINTED
C                          SOLUTION(S) (DEFAULT=0.0  M(N)=10.0).
C          N_IMP     MAXIMUM NUMBER OF IMPURITY/SPURIOUS LINES ACCEPTED AMONG
C                          THE FIRST N LINES [N_IMP takes into account both
C                          impurity lines and peak positions out of the input
C                          absolute angular error EPS].
C                    IF N_IMP <0  THE SEARCH STARTS WITH ZERO IMPURITY LINES,
C                          THEN, IT CONTINUES WITH ONE IMPURITY LINE, AND
C                          SO ON UNTIL 'N_IMP' IMPURITY LINES IS REACHED.
C          ZERO_S    A PRIORI SEARCH FOR A ZERO-POINT ERROR IN INPUT DATA.
C                    =0    NO SEARCH
C                    =1    SEARCH
C                    IF ZERO_S NE 0 OR 1, THEN ZERO_S REPRESENTS A KNOWN
C                          ZERO CORRECTION (e.g. -0.10) IN DEG. 2THETA.
C          ZERO_REF  =0    NO 'ZERO-POINT' LEAST-SQUARES REFINEMENT.
C                    =1    'ZERO-POINT' LEAST-SQUARES REFINEMENT.
C
C          OPTION    =0    DICVOL04 OPTION (OPTIMIZED STRATEGY SEARCH WITH
C                          DECREASING CELL VOLUMES).
C                    =1    OPTION WITH EXTENDED (EXHAUSTIVE) SEARCH IN VOLUME
C                          DOMAINS CONTAINING MATHEMATICAL SOLUTION(S)
C                          (LONGER CPU TIMES).
C                    IF OPTION IS OMITTED, DEFAULT IS DICVOL04.
C
C  CARDS 6 to 6+N_TOTAL   D(I) [,EPSIL(I)]                FREE FORMAT
C
C          (ONE FOR EACH INPUT LINE, FOR ALL N_TOTAL LINES)
C          D(I)     VALUE DESCRIBING THE OBSERVED POSITION OF LINE 'I'
C                   ACCORDING TO SPACING UNIT 'ITYPE'.
C          EPSIL(I) ONLY IF EPS=1.0 (CARD 5): ABSOLUTE ERROR FOR 'D(I)',
C                   ACCORDING TO 'ITYPE', 
C                   [IF EPS= 0.0 OR EPS IS A CONSTANT NOT EQUAL TO 1.0 (e.g.
C                   0.02)(SEE CARD 5), ONLY 'D(I)' ARE REQUIRED].
C  NOTE:
C          IF ITYPE=1,2,4 THE VALUES OF 'D(I)' AND 'EPSIL(I)' MUST
C          BE PREFERABLY (THOUGH IT IS NOT MANDATORY) LISTED IN INCREASING
C          ORDER.
C          IF ITYPE=3 THEY MUST BE PREFERABLY LISTED IN DECREASING ORDER.
C
C      ___________
C      OUPUT FILES
C      -----------
C
C DICVOL06 GENERATES TWO OUTPUT FILES:
C
C          - A FILE CONTAINING THE SOLUTIONS AS FOUND BY THE PROGRAM (ALSO
C            SEEN ON THE DISPLAY WHEN DICVOL06 IS RUNNING).
C          - A SECOND FILE WITH THE SAME NAME AND THE EXTENSION '.ord', IN
C          WHICH ALL (MATHEMATICAL) SOLUTIONS ARE RANKED ACCORDING TO THEIR
C          de WOLFF FOM.
C
C        *****************************************************
C        *                                                   *
C        *               THE USE OF DICVOL06                 *
C        *                                                   *
C        *****************************************************
C
C      USE AS INPUT DATA ALL AVAILABLE DIFFRACTION LINES (N_TOTAL). ONLY THE
C      FIRST N (eg 20, SEE CARD 2) LINES WILL BE USED FOR THE SEARCH OF
C      SOLUTIONS. THESE SOLUTIONS ARE SUBSEQUENTLY USED AUTOMATICALLY FOR
C      REVIEWING ALL N_TOTAL INPUT DATA. THE IMPURITY TOLERANCE 'N_IMP' IS
C      RELATED ONLY TO THE N LINES USED FOR SEARCHING SOLUTION(S) (OF COURSE,
C      OTHER UNINDEXED LINES CAN BE FOUND AMONG THE EXTRA INPUT LINES IN THE
C      REVIEWING PROCESS). BE CAREFUL IN USING THE IMPURITY TOLERANCE:
C      SPURIOUS LINES INCREASES THE RISK TO MISS THE CORRECT SOLUTION!
C
C      ==> WITH GOOD QUALITY DATA, OPTION = 0 (i.e. DICVOL04) IS RECOMMENDED.
C
C      ==>THE OPTION 'EXTENDED (EXHAUSTIVE) SEARCH'  (OPTION =1 IN CARD 5),
C      CAN BE USEFUL IN CASES OF
C       (i) UNSTABLE CASES, i.e. MANY SOLUTIONS ARE FOUND IN A SMALL RANGE OF
C       CELL VOLUMES,
C       (ii) EXPECTED DIFFRACTION LINES ARE MISSING AMONG THE FIRST INPUT
C       LINES,
C       (iii) LOW QUALITY DATA,
C       (iv) SIGNIFICANT NUMBER OF IMPURITY LINES, ETC.
C      IF A SOLUTION IS FOUND IN A VOLUME SHELL, THE SEARCH IS EXHAUSTIVE
C      WITHIN THIS SHELL. THUS, THE SEARCH IS NOT EXTENDED TO THE NEXT VOLUME
C      SHELL (FOR THE SYMMETRY BEING ANALYSED). IF NEEDED, THE USER CAN RUN
C      AGAIN DICVOL06, FOR SELECTED LATTICE SYSTEMS, TAKING THE HIGHER VOLUME
C      VALUE OF THE ALREADY ANALYSED VOLUME SHELL AS 'VOLMIN' IN THE NEW INPUT
C      PARAMETERS SET (CARD 3).
C
C      GENERALLY, RUNS WITH OPTION =1 TAKE LONGER CPU TIMES AND THE NUMBER OF
C      MATHEMATICAL SOLUTIONS IS GREATER (IT HAS BEEN LIMITED TO THE FIRST 100
C      FOUND SOLUTIONS IN THE DICVOL06 OUTPUT FILE). BY ACTING ON THE INPUT
C      FOM (GREATER FOM IN CARD 5) SOLUTIONS WITH LOWEST FOMs CAN BE REJECTED).
C      BE CAREFUL: AS SOON AS 100 SOLUTIONS ARE FOUND THE CALCULATION STOPS.
C
C      DICVOL06 OFFERS THE POSSIBILITY TO ANALYSE YOUR INPUT DATA FOR THE
C      PRESENCE OF A ZERO-POINT ERROR. THE METHOD EMPLOYED CAN SUGGEST MORE
C      THAN ONE OR TWO SOLUTIONS (DUE TO UNCERTAINTY IN SEARCHING HARMONIC
C      DIFFRACTION LINES). THIS OPTION IS TO BE USED PRIOR THE INDEXING
C      PROCESS. PLEASE, AS FAR AS POSSIBLE AVOID THE USE OF THIS FACILITY BY
C      ENSURING THE QUALITY OF YOUR COLLECTED DATA!
C
C      USUAL 'ZERO-POINT' ERRORS (IF NOT TOO BIG) ARE GENERALLY CORRECTED BY
C      THE LEAST-SQUARES REFINEMENT OF THE 'ZERO-POINT' PARAMETER (ZERO_REF IN
C      CARD 5), TOGETHER WITH THE REFINEMENT OF CELL PARAMETERS. ZERO_REF IN
C      CARD 5 IS, IN FACT, AN EXTRA DEGREE OF FREEDOM IN THE REFINEMENT. IT
C      INCLUDES ALL SYSTEMATIC MEASUREMENT ERRORS FROM DIFFRERENT ORIGIN,
C      E.G. ZERO-POINT SHIFT, SAMPLE-SURFACE DISPLACEMENT, UMBRELLA EFFECT,
C      TRANSPARENCY, CAPILLARY DISPLACEMENT, ..
C
C      SUGGESTED STRATEGY:
C      ------------------
C      IT IS RECOMMENDED TO USE A TWO- [1 & 2] OR THREE-STAGES PROCEDURE
C      (i.e. TRICLINIC LATTICES SHOULD PREFERABLY BE STUDIED SEPARATELY), e.g.:
C        1- SEARCH IN HIGH SYMMETRIES DOWN TO ORTHORHOMBIC.
C           CARD 2 : N,ITYPE,1,1,1,1,0,0
C        2- SEARCH IN MONOCLINIC SYMMETRY.
C           CARD 2 : N,ITYPE,0,0,0,0,1,0
C        3- IF NECESSARY, SEARCH IN TRICLINIC SYMMETRY.
C           CARD 2 : N,ITYPE,0,0,0,0,0,1
C
C      NOTE THAT FOR SOLUTIONS WITH MONOCLINIC AND TRICLINIC SYMMETRIES
C      THE PROGRAM PROVIDES THE REDUCED CELL. IF VARIOUS EQUIVALENT SOLUTIONS
C      ARE FOUND, ONLY ONE OF THEM IS LISTED IN THE OUTPUT FILE.
C
C      TRIGONAL SYMMETRY CASE WITH RHOMBOHEDRAL LATTICE: THE PATTERN IS
C      INDEXED WITH AN HEXAGONAL LATTICE, HAVING A UNIT CELL VOLUME THREE
C      TIMES GREATER.
C
C  RECOMMENDATIONS
C  ---------------
C      READ CAREFULLY REFERENCES 1 AND 6 (AND 9), AS WELL AS THIS USER'S
C      GUIDE. PLEASE, SPEND TIME TO ENSURE THE QUALITY OF YOUR COLLECTED DATA
C      (SEE REF. 5). WITH ACCURATE DATA, THE SUCCESS RATE OF DICVOL06 IS VERY
C      HIGH. PEAK POSITIONS SHOULD BE EXTRACTED WITH A PROFILE FITTING
C      SOFTWARE. AN INTERACTIVE PROGRAM SHOULD BE PREFERRED, SINCE AUTOMATIC
C      EXTRACTIONS CAN MISS LINES (LOW INTENSITY, SHOULDER, ..).
C
C      WITH BAD DATA, THE CHANCE TO OBTAIN THE CORRECT SOLUTION IS SMALL AND
C      THE CALCULATION CAN BE TIME-CONSUMING.
C
C      WITH MODERN X-RAY POWDER DIFFRACTOMETERS (THE USE OF MONOCHROMATIC
C      RADIATION IS RECOMMENDED), ABSOLUTE ERRORS ON PEAK POSITIONS LOWER
C      THAN 0.02 DEGREES 2-THETA CAN BE ROUTINELY OBTAINED. FOR INDEXING
C      PURPOSES, ERRORS SHOULD NOT (IDEALLY) EXCEED 0.03 DEG. 2-THETA.
C      [IN EXCEPTIONAL CASES, A FEW LINES WITH GREATER INDIVIDUAL ESTIMATED
C      ERROR CAN BE INTRODUCED IN THE INPUT DATA. IN THIS CASE, USE THE
C      PARAMETER EPS= 1. IN CARD 5, AND ENTER INDIVIDUAL ERRORS AFTER D(I) FOR
C      EACH LINE].
C
C      WITH HIGH RESOLUTION POWDER DIFFRACTION DATA (CONVENTIONAL OR,
C      PARTICULARLY, SYNCHROTRON X-RAY SOURCES), THE ABSOLUTE ERROR IS
C      USUALLY LESS THAN 0.02 (OR EVEN 0.01 WITH ULTRA-HIGH RESOLUTION) DEG.
C      2-THETA; CONSEQUENTLY, EPS=0.02 (OR EVEN EPS=0.01) IS RECOMMENDED; THE
C      CONVERGENCE OF THE DICHOTOMY PROCEDURE WILL BE IMPROVED. HOWEVER, BE
C      SURE THAT THIS CONDITION IS TRUE FOR ALL LINES USED AS INPUT DATA.
C      (REMEMBER THAT ALL MATHEMATICAL SOLUTIONS WITHIN THE INPUT LIMITS AND
C      ERROR BOUNDS ARE FOUND, THE GREATER THEY ARE THE GREATER IS THE NUMBER
C      OF MATHEMATICAL SOLUTIONS).
C
C      ===> N_IMP PARAMETER: N_IMP CAN BE USED IN CASE OF EXPECTED SPURIOUS
C      LINES (i.e. IMPURITY LINES, AS WELL AS OBSERVED LINES OUT OF THE INPUT
C      ERROR). N_IMP ACTS AT ALL SUCCESSIVE LEVELS OF THE DICHOTOMY ALGORITHM.
C      AS SOON AS AN INDEXING SOLUTION IS RETAINED, A LEAST-SQUARES REFINEMENT
C      OF LATTICE PARAMETERS IS CARRIED OUT. FOR THIS REFINEMENT A LARGER
C      ERROR ON OBSERVED LINES IS CONSIDERED. THEN, A LINE REJECTED AT THE
C      LAST DICHOTOMY LEVEL CAN, BY CHANCE, BE ACCEPTED WITH THE REFINED
C      LATTICE PARAMETERS. [EXAMPLE OF POSSIBLE CASE: N_IMP = 0  NO SOLUTION;
C      N_IMP = 1 ONE SOLUTION; HOWEVER, AFTER L-S REFINEMENT OF THE LATTICE
C      PARAMETERS ALL N LINES USED FOR SEARCHING SOLUTIONS ARE INDEXED WITH
C      THE REFINED PARAMETERS.]
C
C      NOTE THAT THE PROGRAM DICVOL06 IS EXECUTABLE FROM 7 LINES- 8 LINES IF
C      THE 'ZERO-SHIFT' IS REFINED - (THOUGH IT IS NOT RECOMMENDABLE SINCE L-S
C      REFINEMENT UNSTABILITIES CAN BE EXPECTED).
C
C      LONG AND SHORT AXIS CASES (DOMINANT ZONE CASES): IF SUCH CASES ARE
C      EXPECTED, THE NUMBER 'N' OF LINES (CARD 2) USED FOR SEARCHING THE
C      SOLUTION SHOULD, GENERALLY, BE GREATER THAN 20.
C
C      THE MINIMUM VALUE FOR A LINEAR LATTICE PARAMETER HAS BEEN FIXED TO 2.5
C      ANGSTROMS.
C
C      RELIABILITY OF INDEXING SOLUTIONS: READ PARAGRAPH 8 OF REF. 5 AND
C      REFS 7 AND 8.
C
C      THE BEHAVIOUR OF THE DICHOTOMY ALGORITHM WITH RESPECT TO THE NUMBER OF
C      LINES REQUIRED FOR INDEXING AND THE CASE OF BIPHASIC MIXTURE IS
C      DISCUSSED IN REF. 6.
C
C      THE LOGICAL FILTERS USED IN DICVOL06 FOR THE SELECTION OF SOLUTIONS
C      ARE DESCRIBED IN REF. 9.
C
C      NOTE THAT WITH THE OPTION DICVOL04 (OPTION =0), AS SOON AS A SOLUTION
C      IS FOUND, ONLY SOLUTIONS WITH SMALLEST VOLUMES WILL BE SUBSEQUENTLY
C      RETAINED. IF (FOR SOME REASONS!) YOU ARE NOT SATISFIED BY THE SOLUTION,
C      YOU CAN RUN AGAIN THE PROGRAM WITH AN INPUT LOWER VOLUME LIMIT SLIGHTLY
C      GREATER THAN THAT OF THE FOUND SOLUTION (THE EXHAUSTIVE SEARCH IS THEN
C      EXTENDED TO A HIGHER VOLUME).
C
C      NOTE THAT THE SEARCH IS EXHAUSTIVE WITHIN THE LIMITS ON THE INPUT DATA. 
C      IN PARTICULAR, THE SEARCH IS CONSTRAINED BY THE HIGHER AND SMALLER
C      BOUNDS ON PARAMETERS, VOLUMES, SELECTED FOM AND ABSOLUTE ERRORS ON PEAK
C      POSITIONS. PLEASE ACT ON THESE PARAMETERS WHEN USING DICVOL06.
C
C      A LATTICE METRIC SINGULARITY OCCURS WHEN UNIT CELLS DEFINING TWO 
C      LATTICES HAVE AN IDENTICAL SET OF CALCULATED d-SPACINGS. THIS CAN
C      BE OBSERVED WITH HIGH SYMMETRY LATTICES (READ REF.5, SECT. 4.2, AND
C      REFS THEREIN). SIMPLE RELATIONS EXIST BETWEEN THE PARAMETERS OF THE TWO
C      CELLS, AS WELL AS PARTICULAR CELL-VOLUME RATIOS. A TYPICAL CASE IS: AN
C      HEXAGONAL CELL [a, c, VOLUME V] CAN BE INDEXED WITH AN ORTHORHOMBIC
C      CELL [PARAMETERS: a/2, a SQRT(3), c, VOLUME V/2]. DUE TO THE STRATEGY
C      USED IN DICVOL, BASED ON AN ANALYSIS THROUGH DECREASING SYMMETRY, ALL
C      CELLS SHOULD BE, IN PRINCIPLE, DISPLAYED IN THE OUTPUT FILE (EXCEPT IF
C      A SOLUTION IS REJECTED BY THE INPUT MAXIMUM VOLUME).
C
C      CHECK ON VALIDITY OF AN INDEXING RESULT: PLEASE READ REF. 5 (SECT. 8)
C
C      POSSIBLE SPACE GROUPS: LOOK AT THE HKL CONDITIONS IN THE OUTPUT
C      LIST OF THE REVIEWING OF THE COMPLETE INPUT DATA PROVIDED AFTER A
C      SOLUTION IS FOUND FROM THE FIRST N LINES.
C
C      ADDITIONAL INFORMATION ON DICVOL06 SHOULD APPEARED IN REF. 9.
C
C
C  REFERENCES
C     1.-  BOULTIF, A. AND LOUER, D., POWDER PATTERN INDEXING WITH THE
C          SUCCESSIVE DICHOTOMY METHOD.
C          J. APPL. CRYST. 37, 724-731 (2004).
C     2.-  LOUER, D. AND LOUER, M., METHODE D'ESSAIS ET ERREURS POUR
C          L'INDEXATION AUTOMATIQUE DES DIAGRAMMES DE POUDRE,
C          J. APPL. CRYST. 5, 271-275 (1972).
C     3.-  LOUER, D. AND VARGAS, R., INDEXATION AUTOMATIQUE DES
C          DIAGRAMMES DE POUDRE PAR DICHOTOMIES SUCCESSIVES,
C          J. APPL. CRYST. 15, 542-545, (1982).
C     4.-  BOULTIF, A. AND LOUER, D., INDEXING OF POWDER DIFFRACTION
C          PATTERNS FOR LOW SYMMETRY LATTICES BY THE SUCCESSIVE
C          DICHOTOMY METHOD, J. APPL. CRYST. 24, 987-993 (1991).
C     5.-  LOUER, D., AUTOMATIC INDEXING: PROCEDURES AND APPLICATIONS, IN
C          'ACCURACY IN POWDER DIFFRACTION II', NIST, SPEC. PUBL. No. 846,
C          GAITHERSBURG, MD, USA, pp. 92-104, 1992.
C     6.-  LOUER, D. AND BOULTIF, A., INDEXING WITH THE SUCCESSIVE DICHOTOMY
C          METHOD, DICVOL04, Z. KRISTALLOGR. 23, 225-230 (2006).
C     7.-  DE WOLFF, P.M., A SIMPLIFIED CRITERION FOR THE RELIABILITY
C          OF A POWDER PATTERN INDEXING, J. APPL. CRYST. 5, 108-113 (1968).
C     8.-  SMITH, G. S. AND SNYDER, R. L., F(N): A CRITERION FOR RATING
C          POWDER DIFFRACTION PATTERNS AND EVALUATING THE RELIABILITY
C          OF POWDER-PATTERN INDEXING, J. APPL. CRYST. 12, 60-65 (1979).
C     9.-  LOUER, D. AND BOULTIF, A., POWDER PATTERN INDEXING AND THE
C          DICHOTOMY ALGORITHM, Z. KRISTALLOGR., IN PRESS (2007).
C
