On-going development work around the GAMESS-UK electronic structure code [1] has included both extensions to the program's functionality and efforts to optimise the performance of the code on current state-of-the-art hardware. Present functionality lies at varying levels of approximation, including scalar relativistic effects, SCF (RHF, UHF, CASSCF, MCSCF, GVB) and DFT, MP2, MP3, MP4, CCSD(T), CI (MRDCI, Direct-CI, Full-CI) and analytic SCF and MP2 second derivatives. The package is currently available on vector hardware, on workstations and on both IA32- and IA64 commodity CPUs from all the leading vendors. Parallel implementations address both MPP (the Cray T3E from Cray/SGI, the SP series from IBM and the Hitachi SR2201) and SMP cluster platforms (notably the Origin 2000 and 3000 series from SGI, Alphaserver SC from Compaq and Cray's prototype Alpha-based Supercluster). Over the last year an extensive evaluation of current High-end supercomputers and Beowulf-class commodity hardware based on Alpha, IA32 (Pentium III and 4 plus AMD’s Athlon) and more recently IA64 processors has been carried out. GAMESS-UK has been one of the central codes for this exercise. There are currently over 140 academic sites and a number of industrial users. Version 6.3 of the code (Version 6.3.2) was finalised in February 2003, and is now distributed as the standard release of the code.

Work around GAMESS-UK during the past 12 months has focused on the following areas:

1. Major work around the DFT module within GAMESS-UK has concentrated on the development of analytic 2^nd derivatives. A thorough investigation of the accuracy in structural predictions of the built-in auxiliary Coulomb Fitting Basis sets (DGauss-A1 and -A2, DeMon and those due to Ahlrichs) has been performed as well.
2. The ZORA module [2] has been updated to use an atomic approximation to the relativistic terms, this approximation curing the tiny gauge invariance errors in the original approach. At the same time it allows for a much more efficient evaluation of the relativistic corrections to the energy and the geometric derivatives of the energy. The strictly atomic ZORA [3] is now the default, giving exact gradients, although the full ZORA treatment is still available. The present implementation only provides for Scalar ZORA, with the Spin-Orbit ZORA still under development.
3. The optimiser module from the Manchester-based CCP1 Flagship QM/MM project has now been incorporated into GAMESS-UK and is being tested for pure QM optimisations.
4. On-going effort improvements continue to be made to the semi-Direct, table-driven CI code due originally to R.J. Buenker. Major reductions have been achieved in the amount of disc space and main memory used by the module, thereby allowing a wider range of systems to be studied. The set of properties offered by the module has been significantly extended.
5. The direct-CI code by Saunders and Van Lenthe has been parallelized using an Global Array based approach.
6. Analytic ECP 2^nd derivatives developed as part of the complete re-write of the ECP code in GAMESS-UK is now available in Alpha release.
7. The NBO analysis has been extended to enable UHF wavefunctions.
8. Integration of the Valence-bond code, Turtle, into GAMESS-UK has been carried out during the past 12 months. An Alpha release of the module is to be released shortly.
9. Further work on QM/MM functionality has been carried out. Coupling of GAMESS-UK to classical systems described by using CHARMM, GULP and DL_POLY packages has been extensively used within the QUASI project. The CHARMM / GAMESS-UK hybrid module has been implemented and validated on the SGI Origin 3800 and Compaq AlphaServer SC, and on a variety of commodity clusters.
10. Significant effort has been invested in preparing a variety of tutorial material for GAMESS-UK. This material was presented in 4 hours of lectures at the Daresbury Chemistry Codes workshop (November 26-28, 2001), and is now available on the CCP1 web-site [4].
11. The long-standing requirement by CCP1 for a free, extensible graphical interface has initiated the development of a GUI based on Python [5]. GAMESS-UK is being used as one of the QC codes to inform functionality requirements.
12. A number of enhancements providing for increased robustness and ease of use include:

• The Global Array and parallel eigen solver (PeIGS) source for parallel builds has been updated, supporting a wider range of platforms.
• Reduced functionality build options (SCF+DFT & MP2) for use on parallel machines with limited node memory, and for benchmark and porting exercises.
• The use of section numbers for specifying the storage and retrieval of eigenvectors can now be omitted.

New Ports of the code to a number of platforms include those for (i) Pentium 4 using Intel’s ifc compiler, (ii) IBM’s power4-based servers, and (iii) HP's Itanium and Itanium 2-based servers. New parallel versions include a tcgmsg-mpi version for the PA-RISC based parallel machines from HP, together with IA32-based systems under both Myrinet and SCALI/SCI interconnects. In addition 64-bit builds are now supported on a range of platforms (Origin, Alpha Linux, AIX, and Solaris).

[1] GAMESS-UK is a package of ab initio programs written by M.F. Guest, J.H. van Lenthe, J. Kendrick, and P. Sherwood, with contributions from R.D. Amos, R.J. Buenker, H.J.J. van Dam, M. Dupuis, N.C. Handy, I.H. Hillier, P.J. Knowles, V. Bonacic-Koutecky, W. von Niessen, R.J. Harrison, A.P. Rendell, V.R. Saunders, A.J. Stone, and D.J. Tozer. The package is derived from the original GAMESS code due to M. Dupuis, D. Spangler and J. Wendoloski, NRCC Software Catalog Volume 1, Program No. QG01

(GAMESS), 1980. M.F. Guest, R.J. Harrison, J.H. van Lenthe and L.C.H. van Corler, Theo. Chim. Acta 71 (1987) 117. M.F. Guest et al., Computing for Science Ltd., CLRC Daresbury Laboratory, Daresbury, Warrington WA4 4AD (http://www.cfs.dl.ac.uk)

[2] S. Faas, J.G. Snijders, J.H. van Lenthe, E. van Lenthe and E.J. Baerends, The Zora formalism applied to the Dirac-Fock equation, Chem. Phys. Lett. 246 (1995) 632.

[3] Chem. Phys. Lett. 328, (2000).

[4] The associated MS PowerPoint presentations are available in both HTML and PDF format at http://www.cfs.dl.ac.uk/tutorials

[5] Python, http://www.python.org