Roy McWeeny
Born May 19, 1924 in Bradford, Yorkshire, England.
Professore Emerito Ordinario di Chimica Teorica, Dipartimento di Chimica e Chimica Industriale dell'Università, Pisa, Italy.
Email:mcweeny@dcci.unipi.it
Member International Academy of Quantum Molecular Science. Member European Academy of Arts, Sciences and the Humanities.
Author of:
Symmetry: An Introduction to Group Theory (Pergamon, Oxford, 1963); Methods of Molecular Quantum Mechanics (with B.T. Sutcliffe) (Academic, London 1969); Spins in Chemistry (Academic, New York, 1970); Quantum Mechanics: Principles and Formalism (Pergamon, Oxford, 1973); Quantum Mechanics: Methods and Basic Applications (Pergamon, Oxford, 1973); Coulson's Valence (Oxford University Press, 1979); Methods of Molecular Quantum Mechanics, 2nd Ed (Academic, London, 1989); with many chapters in multiauthor volumes and about 150 research publications.
Important Contributions:

Calculation of wavefunctions in momentum space; use of gaussian approximations; theory of Compton scattering.

Theory of Xray scattering by bonded atoms; scattering factor calculations with gaussian approximation of Slater orbitals; partitioning of electron density using atom and bond populations; calculation of diamagnetic properties of aromatic systems.

Ab initio VB theory with orthogonalised orbitals; general theory of orbital approximations, electron density and use of reduced density matrices; formulation of master equations for MCSCF calculations.

SCF theory with direct (steepest descent) calculation of the FockDirac density matrix; electronic properties of pelectron systems (ring currents, NMR shielding, electronic spectra).

Introduction of 'groupfunction' theory for description of large molecules; general theory of charge and spin densities and origin of electronic properties, spin Hamiltonians, etc.; first applications of HallRoothaan SCF equations to crystals.

SCF perturbation theory for the FockDirac density; applications to electric and magnetic properties.

Semiempirical schemes for largemolecule calculations; techniques for MCSCF calculations; extensions of the Koopmans theorem.

Theory of spinorbit splitting and g tensors; use of pseudo potentials in valenceelectrononly calculations; manyshell SCF theory in photoelectron spectroscopy.

Timedependent HartreeFock theory for the density matrix; frequency dependent polarizabilities; calculations of dispersion interactions.

General theory of linear response using multiconfiguration TDHF (propagator) methods; applications in intermolecular force calculations; structure of van der Waals complexes.

Development of new forms of ab initio VB theory, with fully optimised nonorthogonal orbitals; applications to reaction surfaces for bondbreaking processes, ionmolecule reactions, and unusual bonding situations; new techniques for ab initioi calculations on large molecules.