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Andrew Crowther Hurley [1926-1988]

Biography

Andrew Crowther Hurley was born in Melbourne on 11 July 1926. His father Victor Hurley, graduated from the University of Melbourne in 1909 with first-class honours in medicine. In August 1914, Victor enlisted in the AIF as a Captain in the Australian Army Medical Corps, serving throughout World War I with great distinction and displaying valuable administrative skills. Subsequently, Victor Hurley became one of the most respected surgeons in Victoria, playing a prominent role in many aspects of medico-political affairs. With the advent of World War II, he was appointed Director General of Medical Services for the RAAF, with the rank of Air Vice-Marshal. In 1950, he was created a Knight Commander of the Order of the British Empire, and in 1952 was given the rare honour for an Australian of election as an Honorary Fellow of the Association of Surgeons of Great Britain and Ireland. Sir Victor Hurley was such a straight-forward and friendly person that it was difficult for his family to understand what a famous man he had become. Those who had known him, referred to his impartiality and fairness; his excellent human relations; and his complete absence of any trace of official arrogance. Many, if not all, of these attributes could be applied to his son Andrew.

Andrew and his three brothers and two sisters grew up at 16 Albany Road, Toorak. ‘Wyuna’ had almost an acre of garden, and was to be the family home for the next twenty-five years. Both the Hurley home and their holiday home at Point Lonsdale had tennis courts, which enabled Andrew to develop as a tennis player. His father was a keen golfer and he and his sons formed a four at bridge.

Andrew’s family soon recognised that he was unusually able. He was neither an avid reader nor a frequent questioner. He enjoyed reading books by Jane Austin, Agatha Christie and Dorothy Sayers, rather than technical reading. His ability to understand seemed to be innate, rather than acquired. As a boy, he would become absolutely engrossed in building ‘incredible things’ with a magnificent set of Meccano. He shared this hobby with a neighbour, who later became a Supreme Court Judge.

In 1934, he commenced at Wadhurst Preparatory School, a junior component of Melbourne Church of England Grammar School (now Melbourne Grammar School) and proceeded to the senior school in 1940. Dr Graham Sargood, who retired from the University of Melbourne as Reader in Physics, recorded some of his memories of Andrew during this period, thus:

I was in the same form as Andrew for every subject in our last four years at school, 1940-43. I remember him as a quiet, undemonstrative, and very approachable boy who seemed to know the answer to every question that ever bothered the rest of us. I recall Andrew pointing out to me at the start of the 1941 school year that there was no need to do the first two assigned physics experiments because the third experiment included all of the measurements needed for the first two, so do the third experiment and then write up all three!

He matriculated in 1942, and completed his Leaving Honours in 1943. He was top student in the state of Victoria in Mathematics I, III and IV, with First Class Honours in Chemistry and Physics.

University education

He enrolled as a student of the University of Melbourne in March 1944. In the first year of a Bachelor of Science degree course, he was top student in Pure Mathematics I, Applied Mathematics I and Physics I, with First-Class Honours in Chemistry IA. His second year results were similarly spectacular, with first place in Pure Mathematics II and equal first in Applied Mathematics II and Physics II. In November 1946, he was awarded the degree of Bachelor of Arts with First-Class Honours and equal first place. His subjects included Pure Mathematics III and Applied Mathematics III. In 1947, Andrew entered the third year of his BSc degree course and obtained Second-Class Honours in Physics III, First-Class Honours in Theoretical Physics and First-Class Honours and first place in Theory of Statistics. He was admitted to the degree of Bachelor of Arts (Honours) on 19 April 1947 and to the degree of Bachelor of Science on 18 December 1948.

In March 1949, he was awarded a Master or Arts degree with First-Class Honours and first place from the School of Mathematics under the supervision of Dr Hans Schwerdtfeger. His thesis was entitled ‘Finite Rotation Groups and Crystal Classes in Four Dimensions’.

The honours that Andrew received at graduation included a CSIRO Studentship and a Dominion and Colonial Exhibition, awarded by the University of Cambridge. In addition, he was awarded a number of other scholarships and exhibitions in the course of his studies. For his golf he was awarded a Half Blue in 1948. However, Andrew’s plans to proceed to Cambridge in 1949 were delayed due to ill health.

PhD at Cambridge 1950-52

From July 1950 to December 1952, he completed his PhD in theoretical physics at the University of Cambridge. He was a member of Trinity College, University of Cambridge, and began his PhD under the supervision of Professor PAM Dirac. Dirac is famous for his contributions to the fundamentals of quantum theory, but he was reputed to be discouraging in his initial contacts with prospective research students. After only one term however, Andrew transferred to the Department of Theoretical Chemistry. This was the first Department of Theoretical Chemistry in the world, which was established in 1932. Its foundation Head, Professor Sir John Lennard-Jones, who was still in charge at the time, was a highly distinguished scientist and administrator.

One reason for transferring to theoretical chemistry was his commitment, under the terms of his studentship, to return to Australia and to work with CSIRO for three years, with the expectation that he would be attached to the Section of Chemical Physics in the Division of Industrial Chemistry. Another reason for this choice may have been his recognition of the huge intellectual strength of the Department of Theoretical Chemistry at that time. Senior members included SF Boys, GG Hall and JA Pople. A 1952 photograph shows seventeen members in all, indicating the high regard of the research community for that department. Andrew would have had a close affinity with Hall, who was primarily a mathematician and who shared Andrew’s interest in group theory. Boys had very recently outlined a new method for obtaining accurate atomic and molecular wave functions based on the use of Gaussian orbitals. Pople was awarded the Nobel Prize in Chemistry in 1998 for his contributions to theoretical chemistry over many years.

His PhD thesis formed the basis of five substantial papers in the Proceedings of the Royal Society of London. Lennard-Jones was co-author of two of these papers. Both Lennard-Jones and Pople were co-authors of the last paper, which is widely recognised as having provided the precursor model of later methods that eventually achieved the practical goal of ‘chemical accuracy’ in variational calculations.

At CSIRO in Melbourne, 1953-54

Andrew returned to Melbourne in January 1953 and commenced work with the Chemical Physics Section of CSIRO’s Division of Industrial Chemistry at Fishermens Bend. At that time, the Division consisted of six Sections namely, Minerals Utilisation, Cement and Ceramics, Chemical Physics, Physical Chemistry, Organic Chemistry and Chemical Engineering. The naming of the Sections was in accordance with the belief of the Chief, Dr (later Sir) Ian Wark, that his Division should carry out a considerable amount of fundamental work.

Andrew was assigned to the Chemical Physics Section, (established in 1945) and whose head was Dr ALG Rees. The initial emphasis was on the acquisition and development of modern physical instruments, both for the benefit of the whole Division, and for conducting independent research. The Section equipped itself to study and apply the techniques of electron microscopy and diffraction, X-ray diffraction and spectroscopy – including mass spectroscopy and infrared spectroscopy. Rees had a personal interest in the chemistry of defect solids and a conviction that the solution to many of the problems in this field would come with a thorough understanding of the quantum physics of those solids.

With a Chief convinced of the importance of fundamental research and a Section head convinced of the importance of theory, and with his own brilliant record, Andrew was warmly welcomed. He was free to pursue his own research, with the proviso that he should be available to provide theoretical support for the experimental work of the Section.

He soon published a series of three papers on the electrostatic calculation of molecular energies and, in 1953, submitted a dissertation to Trinity College, Cambridge and was awarded a four-year Fellowship. Wark was so impressed with Andrew’s summary of his dissertation and with his outline of the direction of research that he wished to pursue that he encouraged members of the CSIRO Executive to read them. After some consideration it was agreed that Andrew should not be required to complete his studentship commitment of three years with CSIRO before taking up the Fellowship. He was duly granted leave of absence from 31 December 1954 to accept the Fellowship for one year, with a possible extension to a second year. It was clear that CSIRO was keen not to lose such a talented scientist and also that Andrew’s immediate superiors appreciated his isolation from the mainstream of theoretical chemistry.

Cambridge 1955-56 and MIT 1957

In March 1955, Andrew returned to Trinity College, Cambridge, as a Title ‘A’ Fellow where he continued his study of Moffitt’s method of atoms in molecules, focusing on how to overcome difficulties that he had identified in his first paper on this subject. He introduced his ‘intra-atomic correlation correction’ and obtained encouraging results for several molecular systems. Andrew’s thorough investigations into the electrostatic method and the method of atoms in molecules were two parts of his overall effort to obtain molecular calculations with chemical accuracy.

While at Cambridge, he received a flattering invitation to spend a year with JC Slater’s Solid State and Molecular Theory Group at the Massachusetts Institute of Technology (MIT). Commencing at MIT in about September 1956, he continued his work on the method of atoms in molecules and put his previously formulated intra-atomic correlation correction onto a more fundamental footing. Andrew benefited greatly from the broad range of interests at MIT. In particular, the strong interest of Slater in crystallographic space groups, together with the presence of Koster, an expert in group theory of both point groups and space groups, sharpened his interest in the application of group theory to problems of the solid state and of molecular physics and chemistry.

CSIRO 1957-88

When Andrew returned to CSIRO at Fishermens Bend on 1 October 1957, he was still the only theoretical chemist in the Chemical Physics Section. His outstanding research achievements during previous years were acknowledged by his almost immediate promotion to Principal Scientific Officer at the relatively early age of 31. Andrew would have found it an exciting time in the Section as the experimentalists, inspired by the leadership of Lloyd Rees and assisted by excellent technical support, strove to become world leaders in their various fields. As evidence of their success, six were to become Fellows of the Australian Academy of Science by 1973 and two also became Fellows of the Royal Society of London. Opportunities for overseas visits greatly helped Andrew to maintain important contacts and to keep abreast of his field.

In 1963, he spent a year as Visiting Lecturer at the Institute for Atomic Research and Department of Chemistry at Iowa State University, Ames. This appointment would fill the vacancy created by the departure of K Ruedenberg for the Johns Hopkins University at Baltimore in Maryland. In addition to carrying out his own research at Ames, Andrew was expected to deliver the lecture courses previously given by Ruedenberg, thus it was a very busy year.

Before returning to Australia in September 1963, he spent six weeks at Johns Hopkins University with Ruedenberg and RG Parr and their research students. In 1964, he was invited to attend the Istanbul International Summer School in Quantum Chemistry, but in this instance, CSIRO declined to make a travel quota position available.

In 1969, he gave a course of sixteen lectures in group theory to the fourth year honours chemistry students at Monash University. From about this time, there was a marked increase in requests to serve as examiner for PhD and DSc degrees, and to provide courses for summer schools in theoretical chemistry. Particularly his Australian colleagues and their students were appreciating Andrew’s qualities of insight more and more. Some recollections by Dr G B Bacskay and Professor P R Taylor illustrate this. George Bacskay was, at that time, a recent graduate of the University of Melbourne and the recipient of a CSIRO studentship. He visited Andrew in 1968, shortly before travelling to Cambridge to ‘read’ for a PhD and recalls:

…on that day at Clayton I met Andrew who told me about his research interests in quantum chemistry, but also about recent developments that made him optimistic about the future of computational quantum chemistry. Much of what he said went right over my head, but he patiently explained, while puffing on his pipe, what I did not understand, or at least admitted to not understanding. He somehow personified my mental image of a ‘theoretician’ that I had built up after reading about the Curies, Bohr and Einstein. That strong positive image stayed with me all my life.

Research interests

Most of Andrew’s research was directed towards the pursuit of chemical accuracy in molecular calculations and the application of group theory to physical and chemical problems. A third group of papers resulted from the application of virial and electrostatic methods. Finally there is a variety of other papers, many stemming from collaborations within the Division of Chemical Physics. Over his career he published a total of 67 papers and two books. Details of this work are provided in the memoir written by VW Maslen, Honorary Retirement Fellow, CSIRO Manufacturing and Infrastructure Technology, Melbourne in 2002 (follow the link in the Sources below).

His two books Introduction to the Electron Theory of Small Molecules and Electron Correlation in Small Molecules, provide a thorough foundation for those wishing to carry out molecular energy calculations of chemical accuracy. In his foreword to Introduction to the Electron Theory of Small Molecules, Andrew expressed the hope that it would provide:

…a ‘royal road’ from basic quantum mechanics, as exemplified by Schrödinger’s wave equation and elementary atomic structure to the various theories and techniques of calculation which today are yielding such detailed information on molecular interactions.

This book provides an account of the basic theory of potential energy curves and surfaces, an outline of the variational method for constructing approximate electronic wave functions and an account of the generalised virial and Hellmann-Feynman formulae and theorems. It also provides a brief but self-contained account of molecular symmetry and extended accounts of the determinantal approach and of molecular orbitals and the Hartree-Fock method. The practical aspects of applications of the theory scattered through the text enriches Andrew’s presentation, and reviewers have remarked on the ‘rich assortment of jewels’. The book includes separate chapters on the hydrogen molecule ion and the hydrogen molecule. Detailed comparisons of different approximate methods applied to those systems make these chapters very informative.

The second book has two chapters. The first chapter introduces theories that overcome the qualitative failures of Hartree-Fock theory; theories that are qualitatively correct for all molecular states and for all molecular geometries. This leads to an instructive comparison of molecular-orbital and valence-bond descriptions and it includes detailed discussions of multi-configuration self-consistent field methods and of the separated electron pair theory pioneered by Hurley, Lennard-Jones and Pople. The second chapter, ‘The correlation problem’, makes up the bulk of the book. Its emphasis is on the succession of pair theories that have taken progressively better account of electron correlation. The chapter includes a reformulation by Andrew of coupled-cluster theory, which was originally introduced to molecular problems by Paldus and Cizek, using diagram techniques. Coupled-cluster theory is regarded as the final step in the inclusion of electron correlation in an orbital-based theory, of which the separated-pair, independent-pair and configuration-interaction approximations were earlier steps. The reformulation proved to be particularly suitable for computation. JA Pople comments as follows:

At the time, we (Pople and colleagues) had completed programming Moller-Plesset (perturbation theory) up to third order and configuration interaction at the doubles level. We were contemplating going to higher orders and also implementing some form of coupled-cluster theory. However, my study of the original papers of Cizek and others left me puzzled about the connections with what we had done on MP2 and MP3. Andrew’s clear presentation in his books and in his personal exposition completely clarified this and I could see the way forward with the inclusion of double substitutions up to fourth order.

Epilogue

Andrew Hurley was positively diagnosed as suffering from emphysema about ten years before his death. However, some of his close friends and colleagues were aware of the symptoms for several years before the official diagnosis. His deteriorating lung condition became increasingly limiting physically. Thus he made use of a mobile golf buggy on the golf course. Later, he avoided travelling to work on ‘smog-alert’ days. He retired from full-time employment in August 1987 and continued bravely as an Honorary Fellow. He died on 18 October 1988. Many colleagues and former colleagues, from both the Division and from the academic world, attended his funeral.

Andrew Hurley was a pure scientist in the fullest sense. He almost invariably followed the solution of a new problem by a search for applications and generalisations, but he never claimed what he could not prove. He deplored pretentiousness. He enjoyed the challenge of new ideas across a broad range of physics, chemistry and mathematics presented in lectures, books and scientific articles and he would sometimes spend extended periods in the library scribbling with pen and paper until he had mastered them. Once, when complimented on his ability to understand a difficult concept, he remarked that anybody could do it: it was just a matter of time! He was a willing ‘tour guide’ to his Division’s experimental projects, in which he showed a keen interest. Andrew also maintained a keen interest in developments across a broad range of mathematics.

Honours and awards

Andrew was elected a Fellow of the Australian Academy of Science in 1971 and was a member of the Australian Mathematical Association from 1957 until his death in 1988.

In April 1989, The International Symposium on Quantum Chemistry, Solid State Theory and Molecular Dynamics dedicated one session to the memory of Andrew. Professor AD Buckingham introduced the session and Dr Peter Taylor delivered the first scientific paper.

Source

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