MOLECULAR SCIENCE

Mol. Sci. 1, A0002 (2007)

ArticleCAT(computer-aided thinking) in chemistry
Sigeru Huzinagaa

The first concerted effort of advancing computationalout that little book entitled “The conservation of orbital

chemistry was put forward at Mulliken’s laboratory in thesymmetry” by Woodward and Hoffmann. The book was a lucid

Department of Physics at the University of Chicago. It was latepresentation of the Woodward-Hoffmann rules. The publication

1950s. Drawing inspiration and substantial benefits fromcaused a commotion among organic chemists in theKotani’s Table of molecular integrals, Ruedenberg andDepartment of Chemistry. One day a senior member of theRoothaan prepared a general mathematical algorism for theOrganic Division walked into my office and said to me, “Wecalculation of one- and two-center molecular integrals over

don’t need anymore to grapple with quantum mechanics. All

STOs. Then, led by Roothaan, a bunch of young people,

we need is to learn the Woodward-Hoffmann theory.” Quite

including Bagus, Clementi, Fraga, Kolos, McLean, Moccia,

probably he meant it as he spoke firmly albeit jokingly.

Ransil, Wahl, Weiss, and Yoshimine, developed a system ofI did not flinch and countered that organic chemists need tocomputer programs for diatomic molecules at the level of thelearn more quantum mechanics, not less, now that the Fukui-

SCF approximation. For the program debugging and also for

Woodward-Hoffmann theory has spectacularly demonstrated,

the production runs, they were flying back and forth between

for the first time, that the wave function ψ itself matters, notChicago and Dayton, Ohio. I joined them in 1958 as a research

indirectly through the electron densityassociate. They were using the UNIVAC computers housed in athat what I said was right. My only regret is that I could notlarge building inside the Wright-Patterson Air Force Base inconvince them of the real usefulness of quantum mechanical

Dayton. Roothaan was certainly a driving force behind thecomputation in order to speculate or to analyze the reaction

molecular computational project but every one in the bunch,mechanism of organic molecular system.

┃ψ┃2 . I still thinksometimes called the Chicago Gang, was driven by one’s own

In the same department Professor Satoru Masamune was

dream and passion to open a new chapter of the computational

making an all-out effort to synthesize cyclobutadiene. It was achemistry. The entire harvest reaped by UNIVAC was vast anddifficult work and I tried my best to offer some theoreticalextensive, including Kolos’ historic work on the hydrogensupport but in those days the computational resources available

molecule. The totality of their achievement was truly amazing

to me was not powerful enough to render him any meaningful

if one thinks of the fact that computers available to the Chicago

help, even for such a small molecule as cyclobutadiene.

Gang in those days were incomparably inferior to today’s

Around 1990 I was toying with the notion of computer-aided

personal computers any school kid can lay his/her hands on,thinking in chemistry. The acronym CAT is an obvious

both in terms of speed and in terms of memory capacity.

imitation of CAD (computer-aided design) widely used in

There was, however, a severe deadlock for the Chicago

various industrial design works. Imagine an office-desk size

project. The problem was in the choice of STOs as thecomputer sitting in an individual research laboratory. The

expansion basis functions. Computations of 3- and 4-centercomputer consists of hard-, firm-, and softwares speciallymolecular integrals over STOs are extremely difficult and thatdesigned to be dedicated to CAT in chemistry and material

impliedmolecularsciences. Needless to say, it should be equipped withcomputations to chemically interesting molecular systems,

virtualimpossibilityofextendinguser-friendly input format and convenient graphic output

including all organic substances and metallic complexes. The

facilities.

only hope appeared to be in the switching of basis set choice

According to what I have learned about a very promisingfrom STOs to GTOs. In 1964 I embarked in earnest on thedevelopmental

preparation of GTO basis sets usable for high quality

Performance Computing system) project, the dream of CAT

multi-center molecular calculations.

may come true sooner than we expect. The project is aptly

In 1968 I started giving a quantum chemistry course at theprojectcalledEAPC(EmbeddedHighdescribed in the following paper: “Development of Special

University of Alberta in Canada. Soon after that, in 1970, camePurpose

aSimulations” by Nagashima, Sasaki, Ohtani, Uehara, Tsukada

Professor emeritus, The University of Alberta, Canada
Correspondence: 5-6-18-1006 Watanabe-Dori, Chuo-Ku, Fukuoka,
Japan 810-0004
e-mail: huzinaga@cup.ocn.ne.jp©Japan Society for Molecular Science

Computersfor

Various

Kinds

ofChemicaland Murakami in J. Comput. Chem. Jpn., Vol 4, No 4 (2005),
131. By the very nature of the project, it is absolutely essential
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(page number not for citation purpose)Mol. Sci. 1, A0002 (2007)
to keep the project robust for a long period of time.

Article(Accepted: March 27, 2007)

Sigeru Huzinaga
Affiliation: Department of Chemistry, Faculty of Science, University of Alberta, Canada
Research field: Computational chemistry, Quantum chemistry
Mailing address: 5-6-18-1006 Watanabe-dori, Chuo-ku, Fukuoka 810-0004
E-mail address: huzinaga@cup.ocn.ne.jp

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