Subject: error/accuracy determinations for S.E. application

From: "Soar, Terri Jacqueline - SOATJ001" <[email-masked]>
Date: Wed, 6 Jan 1999 17:17:35 +1030

Hi CCLers.

I'm after some ideas, pointers or even just people's thoughts as to the topic
of calculating the accuracy of calculations.

This is the situation...For my PhD in physical and inorganic chemistry about
one quarter of my work has involved applying 
computational chemistry. The computational chemistry work has focused on a
range of aluminium-oxyhydroxide species
(monomer, dimer, trimer, tetramer and some polymers) that may exist in aging
caustic aluminate solutions where crystalline
Al(OH)3, i.e. gibbsite, finally precipitates out. 

We are using MOPAC93 with AM1 (i.e. semi-empirical quantum mechanical
methodology) and also with and without COSMO
(to include solvent effects) to perform geometry optimisations and SADDLE
calculations on these species where our main 
interest is the stability and also the relative energetics of the species (wrt
to heats of formation and reaction and also Gibbs
free energy of formation and reaction) to indicate what species are more likely
to exist in these solutions and participate in 
reactions possibly leading to gibbsite formation.

So, how would I go about estimating errors and determining accuracy for this
work (keeping in mind that many of the solution
species we've modelled cannot be measured experimentally (i.e. heats of
formation))? 

As I've said above, I'm after any answers to this question in addition to
people's thoughts as to what may be expected in the way
of accuracy determinations for this type of work.

Thanks in advance and, of course, a summary will be produced.

Terri 
-------------------------------------------------------------------------------
--
Ms. Terri Soar, PhD student,
Ian Wark Research Institute,     tel: +61 8 8302 3706
University of South Australia,    fax: +61 8 8302 3683
The Levels Campus, Mawson Lakes, S.A. 5095, AUSTRALIA
email: [email-masked] <mailto:[email-masked]>