Research Interests

Our research deals with theoretical and computational aspects of molecular and materials sciences, with emphasis on the unified treatment of physical and chemical kinetics using quantum molecular dynamics. It includes collision-induced and photoinduced phenomena in the gas phase, clusters, and at solid surfaces. Our aim is to provide a fundamental approach to molecular dynamics, where electronic and nuclear motions are consistently coupled to account for quantal effects. We use quantum and statistical mechanics, mathematical, and computational methods, to describe time-dependent phenomena (such as femtosecond dynamics and spectra and photoconductivity) in both simple and complex molecular systems. Recent research involves using density matrix methods with applications to optical properties and electronic photoconductivity of materials relevant to photovoltaics. In particular, properties of silicon and of titanium dioxide surfaces with adsorbed silver clusters.

In particular:

Quantum Molecular Dynamics

  • Photoconductivity in nanostructured semiconductors and in quantum dot arrays.
  • Spectra and dynamics of adsorbates on nanostructured semiconductor surfaces.
  • Energy transfer, electron transfer and reactions in molecular collisions and at solid surfaces.
  • Intermolecular forces in ground and excited electronic states.
  • Spectra and dynamics in atomic clusters.
  • Photodissociation of polyatomic molecules.
  • Photodesorption of molecules from solid surfaces.
  • Light emission in collisions of ions with atoms and solid surfaces.

Theoretical Methods

  • Time-dependent many-electron theory; time-dependent molecular orbital and time-dependent Hartree-Fock approaches to molecular phenomena.
  • Density matrix theory of relaxation, dissipation and fluctuations in extended molecular systems.
  • Statistical mechanics of response and rate processes.
  • Few-body and many-body theory of molecular collisions; collisional time-correlation approach to many-atom collisions.

Computational Methods

  • Numerical methods for the solution of the Liouville-von Neumann integrodifferential differential equation for the reduced density operator.
  • Integration of stochastic differential equations for coupled quantal and classical degrees of freedom, and of the generalized Langevin equations.
  • Integration of differential equations for coupled electronic and nuclear degrees of freedom. The “relax-and-drive” method.
  • Calculation of molecular one- and two-electron integrals for travelling atomic basis functions.
  • Numerical methods for the solution of differential and integral equations of scattering.
  • Variational methods for scattering and time-dependent states.
  • Path integral and wavepacket propagation in quantum dynamics.
  • Constrained simulated annealing and constrained molecular dynamics.
  • Operator algebra methods for solving operator differential equations.

Computer Visualization and Animation of Molecular Interactions

  • Animation of the temporal evolution of both nuclear motions and electronic densities using nuclear trajectories and isocontours of electronic densities.
  • Animation of electronic transitions and electron transfer obtained from time-dependent molecular orbitals.
  • Animation of light emission in collisions of ions involving electronic rearrangement and the related transient dipoles.

See also our ongoing research work.