Subject: CCL:MOPAC, bug in POLAR

From: [email-masked] (Dr. James Stewart)
Date: Tue, 13 Dec 94 12:27:03 PST

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