Quantum Chemistry applies the fundamental laws of physics to the study of chemical phenomena at a molecular level. A molecule, is described by a complex mathematical expression called a wavefunction, from which its energy and properties can be determined. By assuming that the particles involved in the molecule are not correlated, wavefunctions for individual particles can be calculated called molecular orbitals and these provide insight into the chemical behaviour of the molecule.
Quantum Chemistry was a major activity of the Harwell Theoretical Physics Group. In consequence, early on, some suites of programs were mounted on Atlas. One of these was MIDIAT which ran on the Risley 7090, the Aldermaston Stretch and the Chilton Atlas. This was one of a set of programs available in the IBM SHARE Library. MIDIAT provided diatomic molecular calculations using Slater-Type Orbitals (STO) which captured the exponential decay accurately but were computationally expensive. Harwell used MIDIAT for two-centre calculations exploring the properties of transition metal salts.
For multi-centre molecular calculations, Gaussian-Type Orbitals (GTO) tended to require less computation despite needing more basis functions.
Vic Saunders had produced a program that used GTOs for the Manchester University Atlas. He joined the Atlas Laboratory in 1970 and provided his system, ATMOL, and other systems for use by UK academics.
Martyn Guest. who had ported the ATMOL code to the CDC 6600 at the Manchester Regional Centre (UMRCC).
joined Vic at the Atlas Laboratory in 1972.
Martyn Guest
Two long term visitors, Jim Browne and Joe Gerratt, added to the large set of programs that were available on Atlas.
With the demise of the Atlas Laboratory, computational chemistry support continued and expanded when it moved to Daresbury in 1976.
(The version of the ATMOL Manual available here is similar to the one used at Chilton, but relates to a port to the UMRCC Cyber 205 in 1982 after the move of ATMOL support to Daresbury.)
Some of the activities in progress at the time of the move to Daresbury were:
In April 1974, an international symposium was organised by the Laboratory at St Catherine's College in Oxford. 41 papers were presented that captured the main problems for computational chemistry.
Jim Browne died on 19 January 2018, aged 83. Obituary
Vic Saunders died on 3 March 2018, aged 74. Obituary
Professor Martyn Guest became Director of Advanced Research Computing at the University of Cardiff in 2007.
