MOPAC, bug in POLAR



              BUG IN MOPAC 93 AND MOPAC 7
 POLAR calculations involving electrooptic Pockels effect (EOPE) and
 optical rectification (OR) give incorrect beta values.
 Second harmonic generation (SHG) beta values are correct.  The fault
 was due to a programming error caused by myself.  The bug was found by
 Prof. Henry Kurtz, one of the authors of the POLAR routine.
 To correct the fault, modify subroutine BEOPOR to replace the line
    COMMON /COORD/  COORD(3,NUMATM)
 with
    COMMON /GEOM /  GEO(3,NUMATM),  COORD(3,NUMATM)
 This correction should be made to all copies of MOPAC 93 and MOPAC 7.
 The fault appeared when iterated beta calculations were done.  The following
 data-sets can be used to verify (1) that the fault exists, and (2) that
 the bug-fix is done correctly.
 James J. P. Stewart.
 ++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++++
 Test data sets:
   POLAR(iwflb=0,beta=1) 1scf
   Formaldehyde
 (Second harmonic generation)
   O    0.00000000  0    0.0000000  0    0.0000000  0    0    0    0     -0.2902
   C    1.21651960  0    0.0000000  0    0.0000000  0    1    0    0      0.2922
   H    1.10612798  0  123.5116221  0    0.0000000  0    2    1    0     -0.0010
   H    1.10612798  0  123.5116221  0  180.0000000  0    2    1    3     -0.0010
   POLAR(iwflb=2,beta=1,gamma=0) 1scf
   Formaldehyde
 (Electrooptic Pockels Effect)
   O    0.00000000  0    0.0000000  0    0.0000000  0    0    0    0     -0.2902
   C    1.21651960  0    0.0000000  0    0.0000000  0    1    0    0      0.2922
   H    1.10612798  0  123.5116221  0    0.0000000  0    2    1    0     -0.0010
   H    1.10612798  0  123.5116221  0  180.0000000  0    2    1    3     -0.0010
   POLAR(iwflb=3,beta=1,gamma=0) 1scf
   Formaldehyde
 (Optical rectification)
   O    0.00000000  0    0.0000000  0    0.0000000  0    0    0    0     -0.2902
   C    1.21651960  0    0.0000000  0    0.0000000  0    1    0    0      0.2922
   H    1.10612798  0  123.5116221  0    0.0000000  0    2    1    0     -0.0010
   H    1.10612798  0  123.5116221  0  180.0000000  0    2    1    3     -0.0010
 Faulty results:
 (Second harmonic generation)
  AVERAGE BETA (SHG) VALUE AT   0.50000 EV =    50.39719
 (Electrooptic Pockels Effect)
   AVERAGE BETA VALUE AT    0.50000 EV =         7.50247
 (Optical rectification)
   AVERAGE BETA VALUE AT    0.50000 EV =         7.55551
    Correct results:
 (Second harmonic generation)
 AVERAGE BETA (SHG) VALUE AT   0.50000 EV =    50.39719
 (Electrooptic Pockels Effect)
   AVERAGE BETA VALUE AT    0.50000 EV =        49.84824
 (Optical rectification)
   AVERAGE BETA VALUE AT    0.50000 EV =        49.85153