Subject: CCL:M:MOPAC for nitrophenols

From: Mario Citra <[email-masked]>
Date: Thu, 6 Feb 97 11:40 EST

S. Shapiro wrote:
"My question is: I am interested in calculating HOMO, LUMO, alpha
polarisabilities, Mulliken partial atomic charges, and dipole moments for 
some nitrophenols of fixed geometry (all optimisation flags = 0).  Should 
one do _all_ of these calculations using the PM3 parametrisation, or just 
some of them?  If AM1 is preferable for some parameters and PM3 for others, 
which parametrisations should be used for which?"

Better to stick with one level of theory for all computed quantities when
comparing a class of compounds.  Since nitrophenols are fairly common
compounds a great deal of experimental data exists for these compounds.  Try
optimizing the geometries and computing physical properties with both AM1
and PM3; then compare calculated values to any experimental data you find.
This should allow you to make a rational judgement about which method to
employ for your fixed point calculations.

Mario J. Citra
MJC
Syracuse Research Corp.