Subject: MOPAC 93 Numerical problems

From: [email-masked] (Mathias Brock)
Date: Mon, 6 Dec 1993 11:25:27 +0100 (MEZ)

Dear netters !

Using MOPAC 93 MNDO on an IBM RS/6000 AIX system at precise level 
repeatly prologation in calculation time occured
by typical numerical problems as below, wasting cpu time.
As far as I know keyword choice is not demanding but problems occur
in special conditions during geometry optimisation i.e. matrix calculation.
Unfortunetely messages are not instructive for trouble shooting, at least
to me.

I should be grateful for suggestions and discussion

M.B.

 MOPAC 93 OUTPUT
 Keywords
 OLDGEO GEO-OK NOINTER DUMP=25H T=24H CHARGE=-12 GNORM=0.1 SCFCRT=0.001 &
 EF MNDO RECALC=2 DDMIN=0.0

 CYCLE:   1 TIME:  74.79 TIME LEFT:  86325.2 GRAD.:    27.661 HEAT:-2961.50
 CYCLE:   2 TIME: 939.27 TIME LEFT:  85385.9 GRAD.:    23.803 HEAT:-2961.500
 CYCLE:   3 TIME:9999.99 TIME LEFT:  74624.8 GRAD.:    16.963 HEAT:-2961.501
 NUMERICAL PROBLEMS IN BRACKETING LAMDA -2488444.18954257946      
 -2488444189.54257965      -2488444.18954506796       
 1720475356.18954229       263070.134841924999
 (similar result with precise- and AM1-keywords)