From chemistry-request@server.ccl.net Sun Jul 25 12:16:52 1999 Received: from alchemy.chem.utoronto.ca (alchemy.chem.utoronto.ca [142.150.224.224]) by server.ccl.net (8.8.7/8.8.7) with ESMTP id MAA31598 for ; Sun, 25 Jul 1999 12:16:52 -0400 Received: (from elewars@localhost) by alchemy.chem.utoronto.ca (8.9.3/8.9.3) id MAA28106 for chemistry@ccl.net; Sun, 25 Jul 1999 12:12:45 -0400 (EDT) Date: Sun, 25 Jul 1999 12:12:45 -0400 (EDT) From: "E. Lewars" Message-Id: <199907251612.MAA28106@alchemy.chem.utoronto.ca> To: chemistry@ccl.net Subject: CPU TIME OVER TIME__AGAIN 1999 July 25 Regarding my posting (below) on the evolution of cpu time, J L Martin (below) posts a correction: for 300 basis functions that should be 6-31G**, not 6-31G*. Thanks. E. Lewars ========================= Hello, M. Esguerra asked: > 21-JUL-1999 13:26:53.94 >From: IN%"esguerra@mentecolectiva.com" "Mauricio Esguerra" >To: IN%"chemistry@server.ccl.net" "ccl" >Subj: CCL:Comp. time vs. Year > > >Hello, > >I want to know if anyone of you knows of any references regarding the >change on the computational time required for some standard ab-initio >calculations like water, benzene, coronene or others, against the year >they were done using the same level of theory and of course taking >advantage of the increase in computational power. > >Thanking your invaluable help, > > >Mauricio Esguerra N. >Grupo de Quimica Teorica >Facultad de Ciencias >Universidad Nacional de Colombia >>=========== The Summer 1993 edition of Gaussian NEWS says: Approx. times for single-point RHF/6-31G* calc on sym-triamino-trinitro- benzene (300 basis functions): Polyatom (ca. 1967) on CDC 1604 200 years (if it would run at all) G80 on VAX 11/780 1 week (if it would run at all) G88 on Cray Y-MP 1 hr on IBM RS/6000 4.5 hr (Model 550) G92 on Cray Y-MP 9 min on Cray C90 4.5 min on IBM RS/6000 1 hr on 486 DX/50 20 hr (a PC) ------ (G98 550 MHz Pentium III ??? --EL) In "The Development of Computational Chemistry in the United States", by J. D. Bolcer and R. B. Hermann, Chapter 1 in _Reviews in Computational Chemistry_, Vol 5 (1994), it is said (page 12) that computers in 1989 were 100 000 (10^5) times faster than in 1959 [Coulson, speaking in 1959 + 30 years]. E. Lewars ====================================================== J M L: PS: that's only 282 basis functions for 6-31G*. 6-31G** would have been 300. --------------------------------------------------------------------- dr. Jan M.L. Martin Senior Lecturer, Computational Chemistry Department of Organic Chemistry/Kimmelman Building, Room 262 Weizmann Institute of Science/IL-76100 Rechovot/ISRAEL Email: comartin@wicc.weizmann.ac.il Phone: +972(8)9342533 Web site: http://theochem.weizmann.ac.il/ FAX: +972(8)9344142 *** finger comartin@winston.weizmann.ac.il for PGP public key *** -- kol ha`olam kulo gesher tzar meod v'ha`ikar lo l'hitpached klal -- ============== From chemistry-request@server.ccl.net Sun Jul 25 12:19:24 1999 Received: from alchemy.chem.utoronto.ca (alchemy.chem.utoronto.ca [142.150.224.224]) by server.ccl.net (8.8.7/8.8.7) with ESMTP id MAA31679 for ; Sun, 25 Jul 1999 12:19:24 -0400 Received: (from elewars@localhost) by alchemy.chem.utoronto.ca (8.9.3/8.9.3) id MAA28315 for chemistry@ccl.net; Sun, 25 Jul 1999 12:15:17 -0400 (EDT) Date: Sun, 25 Jul 1999 12:15:17 -0400 (EDT) From: "E. Lewars" Message-Id: <199907251615.MAA28315@alchemy.chem.utoronto.ca> To: chemistry@ccl.net Subject: CALC IR INTENSITIES__HOW GOOD? 1999 July 25 INTENSITIES OF IR BANDS--HOW GOOD? A lot has been published on correction factors for the *positions* (i.e. the wavenumber values) of calculated IR bands; the canonical paper is A. P. Scott and L. Radom, J. Phys. Chem., 1996, 100, 16502. Has there been any published work on the the *relative intensities* of calculated IR bands? I mean purely empirical comparison of calc and experimental IR spectra, to see which methods give the best match to the real spectra, and how, if possible, one can correct calc intensities to match the experimental. Thanks. E. Lewars ====================