From chemistry-request@ccl.net Sat Mar  7 01:11:40 1992
Date: Fri, 06 Mar 92 23:01:25 -0500
From: radomski@mond1.ccrc.uga.EDU
Subject: Re: A gadfly forever..... (How far can you push semi-empirical
To: chemistry@ccl.net
Status: RO

David Case wrote:

>I too would enjoy hearing from people that know about this.  When I
>wrote a review a few year ago [in "Conformational Analysis of
>Medium-Sized Heterocycles", edited by Richard Glass] semiempirical
>methods seemed to have very poor performance for non-bonded
>interactions and hydrogen bonds -- things that are crucial to most
>peptide and protein simulations.  Errors in barriers to rotation about
>bonds, or in ring conformations (e.g. planar cylcopentane) were also
>common.  But at that time, not much had been published with AM1,
>although that appeared to give improved results in these areas. 

Both AM1 and PM3 yielded almost flat cyclopentane ring when run in full 
geometry optimization mode. The same goes for proline and both ribose
and 2-deoxyribose. Which makes one to ask of what use is 'chemical
meaningfulness' od semi-empirical parameters (as stated recently
by Andy Holder) if the method cannot predict pentose pseudorotation?
To put it differently - how far away is semiempirical parametrization
good enough for flexible ring molecules? 


================================================================
Jan P. Radomski
Department of Biochemistry,
Complex Carbohydrate Research Center,
University of Georgia,
220 Riverbend Rd, Athens GA 30602 USA
e-mail: radomski@mond1.ccrc.uga.edu
================================================================

From chemistry-request@ccl.net Sat Mar  7 02:51:54 1992
Date: Fri, 06 Mar 92 08:36:37 +0900
From: kddlab!vega.rc.m-kasei.co.jp!mei@uunet.UU.NET (Murakami Akinori)
Subject: Re: The future of ab initio
To: chemistry@ccl.net
Status: RO

Thanks to Gaussian inc. and IBM
>>     What would you do if you could ROUTINELY perform ab initio
>>     calculations (let say at the level of HF or HF/MP2) with 500
>>     contracted basis functions?  What kind of projects and
>>     applications would you run?
>>     Jan Labanowski
>>     Ohio Supercomputer Center
>>     
>> HF/6-31G* on C30H62 with no symmetry (574 basis functions) takes well under
>> a day in Gaussian 90 on an inexpensive workstation (RS/6000 model 530).
>> Shouldn't that question be "What applications do you do now that such
>> calculations have been possible for a couple of years?"
>> Michael Frisch
>> Gaussian, Inc.

We have following timing data of Gaussian90 on a IBM RS6000/550 which
is little bit expensive. IBM official Mflops is 25.
					unit[minute]
Molecule	Basis	SCF+grad
C10H8S2		132	28	
C14H12		150	29
C18H12S2	212	109

We are running 200 basis( 20~30 atom) calculation routinely.

But we have to use about 300~500 basis on Metal complex calculation in
our catalyst research.
We want to optimize 500 basis molecule, it will take about 1000 hour 
on 25 Mflops WS. One month for one calculation is not possible in our
research center.

					Akinori MURAKAMI
					Mitusbishi Kasei Corpration
					Yokohama, JAPAN


From chemistry-request@ccl.net Sat Mar  7 12:05:45 1992
Date: Sat, 7 Mar 1992 11:02:19 -0500
From: zheng@retina.chem.psu.EDU (Ya-Jun Zheng)
To: jkl@MPS.OHIO-STATE.EDU
Status: RO

 When I read one of life science journals recently, I noticed that the referee
names were printed together with each paper. This may be a very good idea.

 What do you think?