The Nobel Prize in Chemistry 1998
Walter Kohn, John Pople
My early life was spent in Burnham-on-Sea,
Somerset, a small seaside resort town (population around 5000) on
the west coast of England. I was born on October 31, 1925 and
lived there with my parents until shortly after the end of the
Second World War in 1946. No member of my family was involved in
any scientific or technical activity. Indeed, I was the first to
attend a university.
My father, Keith Pople, owned the principal men's clothing store
in Burnham. In addition to selling clothes in the shop, he used
to drive around the surrounding countryside with a car full of
clothes for people in remote farms and villages. He was
resourceful and made a fair income, considering the economic
difficulties during the depression of the 1930s. My
great-grandfather had come to Burnham around 1850 and set up a
number of local businesses. He had a large family and these were
split up among his children. As a result, I had relatives in many
of the other businesses in the town. My grandfather inherited the
clothing shop and this passed to my father when he returned from
the army at end of the First World War.
My mother, Mary Jones, came from a farming background. Her father
had moved from Shropshire as a young man and had farmed near Bath
for most of his life. I suspect that he would have preferred to
be a teacher, for he had a large collection of books and
encyclopedias. He wanted my mother to be a schoolteacher, but
this did not happen. Instead, she became a tutor to children in a
rich family and, later, a librarian in the army during the first
war. Most of her relatives were farmers in various parts of
Somerset and Wiltshire so, as small children, my younger brother
and I spent much time staying on farms.
Both of my parents were ambitious for their children; from an
early age I was told that I was expected to do more than continue
to run a small business in this small town. Education was
important and seen as a way of moving forward. However,
difficulties arose in the choice of school. There was a good
preparatory school in Burnham but, as part of the complex English
class system, it was not open to children of retail tradesmen,
even if they could afford the fees. The available alternative was
unsatisfactory and my parents must have agonized over what to do.
Eventually, they decided to send us to Bristol Grammar School
(BGS) in the nearest big city thirty miles away. BGS was the
prime day school for boys, catering mainly to middle class
families resident in the city, although it received a government
grant for accepting about thirty boys a year from the state
elementary schools. I went there in the spring of 1936 at the age
of ten. Some arrangement had to be made for boarding and I used
to return home by train each weekend. This I found unappealing
and eventually I persuaded my parents to allow me to commute
daily - two miles by bicycle, twenty-five miles by train and one
mile on foot. I continued to do this during the early part of the
war, a challenging experience during the many air attacks on
Bristol. Often, we had to wend our way past burning buildings and
around unexploded bombs on the way to school in the morning. Many
classes had to be held in damp concrete shelters under the
playing fields. In spite of all these difficulties, the school
staff coped well and I received a superb education.
At the age of twelve, I developed an intense interest in
mathematics. On exposure to algebra, I was fascinated by
simultaneous equations and rapidly read ahead of the class to the
end of the book. I found a discarded textbook on calculus in a
wastebasket and read it from cover to cover. Within a year, I was
familiar with most of the normal school mathematical curriculum.
I even started some research projects, formulating the theory of
permutations in response to a challenge about the number of
possible batting orders of the eleven players in a cricket team.
For a very short time, I thought this to be original work but was
mortified to find n! described in a textbook. I then
attempted to extend n! to fractional numbers by various
interpolation schemes. Despite a lot of effort, this project was
ultimately unsuccessful; I was angry with myself when I learned
of Euler's solution some years later. However, these early
experiences were valuable in formulating an attitude of
persistence in research.
All this mathematical activity was kept secret. My parents did
not comprehend what I was doing and, in class, I often introduced
deliberate errors in my exercises to avoid giving an impression
of being too clever. My grades outside of mathematics and science
were undistinguished so I usually ended up several places down in
the monthly class order. This all changed suddenly three years
later when the new senior mathematics teacher, R.C. Lyness,
decided to challenge the class with an unusually difficult test.
I succumbed to temptation and turned in a perfect paper, with
multiple solutions to many of the problems. Shortly afterwards,
my parents and I were summoned to a special conference with the
headmaster at which it was decided that I should be prepared for
a scholarship in mathematics at Cambridge University. During the remaining
two years at BGS, I received intense personal coaching from
Lyness and the senior physics master, T.A. Morris. Both were
outstanding teachers. The school, like many others in Britain,
attached great importance to the placement of students at
Oxford or
Cambridge. Most such awards were in the classics and I think that
the mathematics and science staff were very anxious to compete.
Ironically, during the last two years at BGS, I abandoned
chemistry to concentrate on mathematics and physics. In 1942, I
travelled to Cambridge to take the scholarship examination at
Trinity
College, received an award and entered the university in
October 1943.
In the middle of the war, most young men of my age were inducted
into the armed forces at the age of seventeen. However, a small
group of students in mathematics, science and medicine was
permitted to attend university before taking part in wartime
research projects such as radar, nuclear explosives,
code-breaking and the like. This was a highly successful project
and many of my predecessors in earlier years made important
contributions to the war effort. The plan was to complete all
degree courses in only two years, followed by secondment to a
government research establishment. In my case, I completed Part
II of the mathematical tripos in May 1945, just as the European
war was ending. In fact, it was hard to concentrate on the
examinations because of the noisy celebrations going on in the
streets outside. The government no longer had need for my
services and the university was under great pressure to make room
for the deluge of exservicemen as they were demobilized from the
armed forces. So, I had to leave Cambridge and take up industrial
employment for a period. This was with the Bristol Aeroplane
Company, close to where I had attended school. There was little
to do there and I had a period of enforced idleness as changing
employment was illegal at the time (part of the obsession for a
planned economy in postwar Britain).
In 1945, I had little idea of what my future career might be. My
interest in pure mathematics began to wane; after toying with
several ideas, I finally resolved to use my mathematical skills
in some branch of science. The choice of a particular field was
postponed, so I devoted much of my time to pestering government
offices for permission to return to Cambridge and resume my
studies. In the late summer of 1947, I finally received a letter
informing me that an unexpectedly large number of students had
failed their examinations and a few places were available. So, in
October 1947, I returned to Cambridge to begin a career in
mathematical science.
Cambridge in 1947 had greatly changed since 1943. The university
was crowded with students in their late twenties who had spent
many years away at the war. In addition, the lectures were given
by the younger generation who had also been away on research
projects. There was a general air of excitement as these people
turned their attention to new scientific challenges. I remained
as a mathematics student but spent the academic year 1947-8
taking courses in as many branches of theoretical science as I
could manage. These included quantum mechanics (taught in part by
Dirac), fluid
dynamics, cosmology and statistical mechanics. Most of the class
opted for research in fundamental areas of physics such as
quantum electrodynamics which was an active field at the time. I
felt that challenging the likes of Einstein and Dirac was
overambitious and decided to seek a less crowded (and possibly
easier) branch of science. I developed an interest in the theory
of liquids, particularly as the statistical mechanics of this
phase had received relatively little attention, compared with
solids and gases. I approached Fred Hoyle, who was giving the
statistical mechanics lectures (following the death of R.H.
Fowler). However, his current interests were in the fields of
astrophysics and cosmology, which I found rather remote from
everyday experience. I next approached Sir John Lennard-Jones
(LJ), who had published important papers on a theory of liquids
in 1937. He held the chair of theoretical chemistry at Cambridge
and was lecturing on molecular orbital theory at the time. When I
approached him, he told me that his interests were currently in
electronic structure but he would very possibly return to liquid
theory at some time. On this basis, we agreed that I would become
a research student with him for the following year. Thus, after
the examinations in June 1948, I began my career in theoretical
chemistry at the beginning of July. I had almost no chemical
background, having last taken a chemistry course at BGS at the
age of fifteen. Other important events took place in my life at
this time. In late 1947, I was attempting to learn to play the
piano and rented an instrument for the attic in which I lived in
the most remote part of Trinity College. The neighbouring room
was occupied by the philosopher Ludwig Wittgenstein, who had
retired to live in primitive and undisturbed conditions in the
same attic area. There is some evidence that my musical efforts
distracted him so much that he left Cambridge shortly thereafter.
In the following year, I sought out a professional teacher. The
young lady I contacted, Joy Bowers, subsequently became my wife.
We were married in Great St. Mary's Church, Cambridge in 1952,
after a long courtship. Like many other Laureates, I have benefit
immeasurably from the love and support of my wife and children.
Life with a scientist who is often changing jobs and is
frequently away at meetings and on lecture tours is not easy.
Without a secure home base, I could not have made much progress.
The next ten years (1948-1958) were spent in Cambridge. I was a
research student until 1951, then a research fellow at Trinity
College and finally a lecturer on the Mathematics Faculty from
1954 to 1958. Cambridge was an extraordinarily active place
during that decade. I was a close observer of the remarkable
developments in molecular biology, leading up to the double helix
papers of Watson and Crick. At the same
time, the X-ray group of Perutz and Kendrew (introduced to
the Cavendish Laboratory by Lawrence Bragg) were
achieving the first definitive structures of proteins. Elsewhere,
Hoyle, Bondi and Gold were arguing their case for a cosmology of
continuous creation, ultimately disproved but vigorously
presented. Looking through the list of earlier Nobel laureates, I
note a large number with whom I became acquainted and with whom I
interacted during those years as they passed through
Cambridge.
In the theoretical chemistry department, LJ was professor and
Frank Boys started as lecturer in September 1948. I began
research with some studies of the water molecule, examining the
nature of the lone pairs of electrons. This was an initial step
towards a theory of hydrogen bonding between water molecules and
a preliminary, rather empirical study of the structure of liquid
water. This fulfilled my initial objective of dealing with
properties of liquids and gained me a Ph.D. and a research
fellowship at Trinity College. This highly competitive stage
accomplished, I was able to relax a bit and formulate a more
general philosophy for future research in chemistry. The general
plan of developing mathematical models for simulating a whole
chemistry was formulated, at least in principle, some time late
in 1952. It is the progress towards those early objectives that
is the subject of my Nobel lecture.
At that early date, of course, computational resources were
limited to hand calculators and very limited access to motorized
electric machines. So my early notes show attempts to simplify
theories enough to turn them into practical possibilities. The
work paralleling studies of Pariser and Parr led to what became
known as PPP theory. This was not a complete model but rather one
applicable to systems with only one significant electron per
atom. It did fit the general form of conjugated hydrocarbons and
achieved some notoriety. In 1953, Bob Parr came to Cambridge to
spend a year with Frank Boys. We shared an office and had many
valuable discussions; he was to have a major influence on my
future. I talked about PPP theory when I began to speak at
international meetings in 1955.
In addition to the PPP work, I started theoretical work on other
topics in physical chemistry. I began supervision of research
students in 1952, beginning with David Buckingham, who completed
a masterly thesis on properties of compressed gases. He was the
first of a long list of remarkably able and dedicated students
who have worked with me over the years. In 1954, LJ was succeeded
as professor of theoretical chemistry by Christopher
Longuet-Higgins, who was joined by Leslie Orgel shortly
afterwards. I continued to spend a lot of time in the chemistry
department, although by then I had undertaken new teaching
responsibilities as a lecturer in mathematics. The department was
crowded and active in those years. Among the many visitors were
Linus Pauling,
Robert
Mulliken, Jack Kirkwood, Clemens Roothaan and Bill Schneider.
Frank Boys was also managing a lively group of students.
At the end of 1955, I developed an interest in nuclear magnetic
resonance, which was then emerging as a powerful technique for
studying molecular structure. At the urging of Bill Schneider, I
agreed to spend two summers (1956 and 1957) at the National
Research Council in Ottawa, Canada, working on the theoretical
background of NMR. This was extremely stimulating for, at that
time, we were measuring the spectra and interpreting the nuclear
spin behaviour of many standard chemicals for the first time. My
time there with Bill and Harold Bernstein led to a book, High
Resolution Nuclear Magnetic Resonance, which was well
received. This area was the main emphasis of my research during
the final years in Cambridge.
By 1958, I had become dissatisfied with my mathematics teaching
position at Cambridge. I had clearly changed from being a
mathematician to a practicing scientist. Indeed, I was
increasingly embarassed that I could no longer follow some of the
more modern branches of pure mathematics, in which my
undergraduate students were being examined. I therefore resolved
to seek a new job with greater scientific content. After some
hesitation, I accepted a position as head of the new Basics
Physics Division at the National Physical Laboratory near London.
This involved direction of experimental work and a considerable
amount of administration. When I took the job, I hoped that the
administrative burden would not be large enough to interfere with
my research programme. Although I was given plenty of help, this
turned out not to be so and I had a rather fallow period while I
was there.
In the spring of 1961, I organized an international conference in
Oxford, along with Charles Coulson and Christopher
Longuet-Higgins. Bob Parr was an invited speaker and, during a
break, he urged me to come and spend a sabbatical year at
Carnegie Institute of Technology in Pittsburgh. This was an
attractive suggestion and I arranged to come for the academic
year 1961-2 with my family. By this time, Joy and I had three
children and were expecting a fourth. We arrived in September,
accompanied by a charming young Swedish au pair, Elisabeth
Fahlvik. One of the most delightful side-effects of winning the
Nobel Prize is the opportunity to meet her again after a gap of
over thirty-six years.
By the time we arrived in Pittsburgh, Bob Parr had decided to
leave for Johns
Hopkins University and he did, in fact, leave in January.
Nevertheless, we had a delightful year, travelling as a family
over much of the eastern part of the U.S.A. During this period, I
made up my mind to abandon my administrative job and seek an
opportunity to devote as much time as possible to chemical
research. I was approaching the age of forty, with a substantial
publication record, but had not yet held any position in a
chemistry department. When we returned to England in June, 1962,
it was not clear where we might go for there were opportunities
both in the U.K. and the U.S.A. Eventually, after much debate, we
decided to return to Pittsburgh in 1964. Leaving England was a
painful decision and we still have some regrets about it.
However, at that time, the research environment for theoretical
chemistry was clearly better in the U.S.
On my return to Pittsburgh, I resolved to go back to the
fundamental problems of electronic structure that I had
contemplated abstractly many years earlier. Prospects of really
implementing model chemistries had improved because of the
emerging development of high-speed computers. I was late in
recognizing the role that computers, would play in the field
– I should not have been, for Frank Boys was continually
urging the use of early machines back in Cambridge days. However,
by 1964, it was clear that the development of an efficient
computer code was one of the major tasks facing a practical
theoretician and I learned the trade with enthusiasm. Mellon
Institute, where I had an adjunct appointment, acquired a Control
Data machine in 1966 and my group was able to make rapid progress
in the dingy deep basement of that classic building. In 1967,
Carnegie Tech and Mellon Institute merged to become Carnegie-Mellon
University (CMU) and I remained on the faculty there until
1993. Almost all of the work honored by the Nobel Foundation was
done at CMU. That institution deserves much of the credit for
their continuing support and encouragement over many years.
The scientific details of the Pittsburgh work are related, in
part, in the accompanying lecture. Over the years, we were able
to keep abreast with the rapid developments in computer
technology. Around 1971, the work was moved to a Univac 1108
machine and then, in 1978, we were fortunate enough to acquire
the first VAX/780 minicomputer from the Digital Equipment
Corporation for use entirely within the chemistry department.
This became a valuable workhorse as we began to distribute
programs to the general chemical community. In more recent years,
of course, the techniques have become available on small work
stations and personal computers. The astonishing progress made in
computer technology has had profound consequences in so many
branches of theoretical science.
Our children were mostly brought up and educated in the Churchill
suburb east of Pittsburgh. Each summer, we took them back to
England for an extended period. By 1979, all had gone away and
Joy and I decided to move again to Illinois, where our daughter
had settled. In 1981, we set up house in Rogers Park, Chicago and
then moved to Wilmette in 1988. Our family is now scattered in
Chicago, Houston, Pittsburgh and Cork, Ireland. We have been
blessed with ten grandchildren (an eleventh expected), who
greatly enrich our lives in many ways.
From 1981 to 1993, I continued to run my research group in
Pittsburgh, commuting frequently and communicating with my
students by telephone and modem. Northwestern
University kindly offered me an adjunct appointment and I
became a full member of their faculty in 1993. I am very grateful
to them for the opportunity to continue my research programme and
interact with other members of the chemistry department.
I have had many opportunities to visit universities all over the
world in the past fifty years. Among the most rewarding have been
frequent trips to Australia and New Zealand, where Joy and I have
wintered no fewer than nine times since 1982. The campus of the
Australian
National University, where Leo Radom became Professor after
spending time with me as a postdoctoral fellow from 1968 to 1972,
has become a second academic home – a great place for
relaxed contemplation.
Israel and Germany are other countries with which I have become
closely associated, having visited and collaborated many times.
In the 1980s, I held a von Humboldt Award, which allowed me to
spend some time in Erlangen, where I collaborated with Paul
Schleyer on a large number of applications of the theory. In
Israel, I have visited and lectured at all universities,
including a period as Visiting Professor at the Technion, Haifa.
In 1992, I was fortunate enough to receive the Wolf Prize in
Chemistry at a ceremony in the Knesset.
I must emphasize that my contribution to quantum chemistry has
depended hugely on work by others. The international community in
our field is a close one, meeting frequently and exchanging ideas
freely. I am delighted to have had students, friends and
colleagues in so many nations and to have learned so much of what
I know from them. This Nobel Award honours them all.
From Les Prix Nobel. The Nobel Prizes 1998, Editor Tore Frängsmyr, [Nobel Foundation], Stockholm, 1999
This autobiography/biography was written at the time of the award and later published in the book series Les Prix Nobel/Nobel Lectures. The information is sometimes updated with an addendum submitted by the Laureate.
John Pople died on March 15, 2004.
Copyright © The Nobel Foundation 1998