Subject: summary: 'low cost' methods available ?

From: <[email-masked]>
Date: Mon, 3 Apr 1995 08:53:24 +0200 (MESZ)

Dear colleguages,

now there is the summary of my recent inquiry about 'low-cost' methods.
My pleasant thank to all the people who answered me.

My original posting:

Dear colleagues,

I'm trying to model the key steps of catalytic reactions involving one or several
transition metal atoms (for the present only 1st row TM atoms are involved).
Because of the largeness of the systems ab-initio techniques (HF-, post-HF or DFT)
can only be applied to distict pre-evaluted key structures (or simplfied models)
wich are previously examined by any lower cost methods. Such methods are the 
common semiempirical approaches (CNDO, ZINDO, NDDO-type methods, ...) or maybe
force field methods, but they should yield reliable enough results. 
Our experiences with ZINDO are not so encouranging because they not give the 
desired accuracy of the results.

We are mainly interested in describing the interaction of saturated/unsaturated 
hydrocarbons with nickel.
So there is my question. Are there any recommended 'low cost' methods available
that can be used side by side with ab-initio techniques in order to get a
basic knowledge of the potential energy surface, that can be used in further
examinations by ab-initio methods ? 
Is there a way out to self-contruct an appropriate force field for nickel describing
the structural and energetical behaviour of some model systems obtained by 
ab-initio methods ?

Any hints, suggestions or pointers are highly appreciated.
Regards

	Peter

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From: [email-masked] (Joe M Leonard)

Spartan V4.0 has implemented Thiel's MNDO/d formalism for both MNDO
and PM3 parameter sets.  Ni has been included in the first set of Trans.
Metals for PM3(tm)...  Have you seen Spartan in the past?  Would
you like additional information?

Joe Leonard
[email-masked]
[email-masked]

------------------------------------------------------------------------------------
From: [email-masked]

Dear Peter,

I saw your note in the CCL for a low-cost
semiempirical/MM program for working with
1st row transition metal complexes.

Have you ever tried PRDDO (Partial retention
of diatomic Differential overlap) program
. It is a program well tested for transition
metals (especially 1st row) complexes by
Dennis Marynick's group at Univ. of Texas at Arlington
, Arlington, Texas. 

If u need further info about Dennis I can 
pass on the info. 

pavan

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From: [email-masked] (Dave Young)

Hi,

	Please post a summary of your replies.

	I can't give you much hope, however.  We do transition metal
systems at high levels of theory (multi-reference CI) and have found
even simple things like HF to be pretty useless.  

	Occassionally you will find a mechanics calculation where
someone has parameterized the metal to behave correctly, but only for that
one specific corridination environment.  Trying to ask mechanicstic 
questions in this type of format generally range from very crude
to totally useless.

	Good Luck.

				Dave Young
				[email-masked]

-------------------------------------------------------------------------------------------
Subject: Re: CCL:'low cost' methods available ?

        Dear Peter,

        There are some ways to do what you want, som hard and some less
hard, but it may be difficult to assess the reliability in advance.
Starting with the easiest to implement, there have just recently become
available some new semi-empirical methods that are especially well suited
for transition metals.  The first of these, and the bases for other
implementations, is Thiel's MNDO-d.  I have only experience with PM3(tm) in
Spartan, I know it is parameterized for nickel.  This is in Spartan 4.0,
which was announced today!  There, you will also have access to DFT from
the same interface.  I only made a few quick tests with nickel, but I'm
satisfied with the accuracy in palladium calculations, in both PM3 and DFT.
        As for force field methods, that is definitely possible.  If you
can't find something that works, you should be able to implement your own
force field for a limited range of nickel complexes without too much
difficulty.  You will be able to calculate you complex immediately with
UFF, available in Cerius2 from Molecular Simulation.  However, my
experiences with this force field are mixed.  Some complexes are very well
treated, whereas others just give junk.  You will just have to try to see
if your complex is one where you can get reliable results.  The same is
true about ESFF in Insight.  I know that a few other programs are
parameterized for some metals (eg. PCModel), but I have no experience of my
own.
        If you can't find anythin that works without modification, I would
suggest that you parameterize a program that can handle the required
coordination on the metal.  I have best experience with MM2* and MM3* in
MacroModel, but also some with MM3 (I'm using Allingers code with the
MacMimic package).  I have heard Dr. Allinger talk about an MM3
specifically parameterized to reproduce ab initio (6-31G*), not
experimental geometries.  That may be your best option, but you'll have to
contact Dr. Allinger directly for it.  MM3 is also one of the few force
fields that is able to reproduce nonstationary low-energy points on the
energy hypersurface (others are CFF and, I believe, Halgrens MMFF).

        Regards,

        Per-Ola Norrby

 *  Per-Ola Norrby
 *  The Royal Danish School of Pharmacy, Dept. of Med. Chem.
 *  Universitetsparken 2, DK 2100 Copenhagen, Denmark
 *  tel. +45-35376777-506, +45-35370850    fax +45-35372209
 *  Internet: [email-masked], [email-masked]

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From: "Dr. Jan Hrusak" <[email-masked]> (in german)

Hallo Peter,

wir haben in den letzten drei Jahren an aehnlichen Problemen 
gearbeitet. (d.h. TM Reaktionen  mit liganden) es ist eine sehr 
hartes Brot wenn man eine gewisse genauigkeit erwartet. Unsere 
erfahrung zeigt, dass man die semiempirischen Verfahren schlicht 
vergessen kann.  Force field Methoden  sind manchmal gute startpunkte 
aber wie kann man eine dative Bindung und/oder Bindungsbruch 
beschrieben? 
Die DFT (oder DFT /HF) methoden (mit RECP) scheinen die ainzige 
Alternative zu sein.
Wir haben fast fuer alle TM metalle 3d, 4d, 5d einschliesslich der
Lanthanide Testrechnungen durchgefuehrt und die Uebereinstimmung mit 
qualitativ hoeheren (CCSDT)) daten ist verbluffend gut. Weiterhin ist 
die Basisatzkonvergenz der Ergebnisse viel schneller als bei SCF oder 
gar CI Methoden. D.h. man kann gute Geometrieabschaetzung mit DZ(p) 
machen und dan auf dieser Geometrie eine single point Rechnung mit 
einer besseren Basis Durchfuehren. Der Aufwandt ist c. das 1.5 fache 
einer SCF. Sicher kann man auch hier auf Grenzen hinsichtlich der 
Groesse stossen , aber wir haben ohne groessere Probleme eine 
vollstaendige (C1 Symmetrie ) Optimierung fuer Systeme Fe+(C10Hn) 
n=10, 12, 14 oder Au+ (Buten, Benzen) durchstehen koennen.
die ergebnisse sind bedeutend besser, als sie mit einer anderen 
Methode sein koennen.

Gruesse 

Jan

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Once again, many thankx to all people who responded.
Regards

	Peter