From jkl@ccl.net Tue Mar 3 14:51:03 1992 To: chemistry@ccl.net Subject: The future of ab initio Date: Tue, 03 Mar 92 14:50:56 EST From: jkl@ccl.net Status: R Dear netters, We, in the Ohio Supercomputer Center, are trying to predict the trends and needs in computational chemistry of the (near) future. And as usual, there are more questions than answers. I have a big favo(u)r to ask. Please, answer me the following question: 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? Can you think about any commercial R & D applications where ab initio methods are important at this level. Thank you very much in advance. Mail it to me (jkl@ccl.net), and I will summarize the responses. Jan Labanowski Ohio Supercomputer Center 1224 Kinnear Rd Columbus, OH 43212-1163, USA jkl@ccl.net JKL@OHSTPY.BITNET From chemistry-request@ccl.net Tue Mar 3 17:18:58 1992 Date: Tue, 03 Mar 92 16:26:19 EST From: Jack Houser Subject: Charge calculations To: Supercomputer bulleti n board Status: R Greetings: Andy Holder's discussion on AM1 vs PM3 charge calculations was interesting and informative. It seems to me that someone, somewhere, sometime must have published a more complete comparison of charge densities calculated by the various semiempirical methods and ab-initio. Could somebody out there give me a reference or at least point me in the general direction? Thanks, Jack Houser From chemistry-request@ccl.net Tue Mar 3 20:37:01 1992 Date: Tue, 3 Mar 92 18:38:13 EST From: m10!frisch@uunet.UU.NET (Michael Frisch) Subject: Re: The future of ab initio To: chemistry@ccl.net Status: R 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. ------- From chemistry-request@ccl.net Wed Mar 4 07:16:50 1992 Date: 04 Mar 92 10:47:02 EDT From: Subject: Large scale computations To: chemistry@ccl.net Status: R E. M. EVLETH Dynamique des Interactions Moleculaires Universite Pierre et Marie Curie 4 Place Jussieu, Tour 22, Paris 75005 (1) 44 27 42 08 UDIM018 at FRORS31 Although Dr. Labanowski requested reponse his large scale computation question to be sent to his own address, Mike Frisch's comment on using G90 on this size permitted me to respond with a question. First, a lot of people will be doing large scale calculations of the 500 CGTO size in the future as well as presently, and routinely. We are working on zeolite substructures and reactions occurring on these models, and that gets big. Certain transition states are correlation sensitive and given the "ifyness" of using a model system our protocols for the present will not go beyond SCF DZP optimizations followed by a MP2 estimate. Currently distributed codes like Gaussian90 can handle this kind of calculation in direct. Note that it is not so much the single point calculation time which is en jeux but the geometry optimization times. Even for relatively small systems these can go on for days or weeks in work station environments. It would also be useful to have work station clusters capable of speeding up that operation. Now the question and remark. The supercomputer environment is one configuration but people are building up clusters of work stations. In some types of problems (molecular dynamics, quantum Monte Carlo) some people are running 20 or more RS/6000 on the same problem. Many labs or Universities have unused units in the night, weekend or vacation periods and those who have work to do groan when they see a machine inactive. Where are people going on this type of clustering with regard to "standard" quantum chemistry codes, especially in direct SCF or MP2? This is of current interest in France and plans are to go "cluster" for the next few years. Any information from the other side of the Atlantic would be appreciated. E. M. Evleth