# Experts in: Thermal properties of small particles, nanocrystals, nanotubes and other related systems

### DHARMA-WARDANA, Chandre

Professeur associé

- Quantum mechanics
- Quantum statistical mechanics
- Raman spectra of III-V and II-VI semiconductors
- Electron-phonon interactions
- Optical properties of nanoscale materials and structures
- Thermal properties of small particles, nanocrystals, nanotubes and other related systems
- Graphene

Professor Dharma-wardana has worked on a wide variety of scientific topics, where the unifying theme is the application of the quantum theory, usually to many-body problems. His work focused on quantum theory, statistical mechanics, and solid state physicsassociated with Raman scattering, energy-relaxation and phonons in nanostructures, quantum Hall effect, the physics of nanotubes and graphene. He worked on a variety of topics such as surface passivisation, quantum dots, organic light-emitting diodes and related nanostructures, energy-relaxation etc., in collaboration with researchers at the NRC, Universities or research institutions in Montreal, Toronto, British Columbia, Livermore, Los Alamos and Paris. A main area of Prof. Dharma-wardana's research has been in many-body theory and plasma physics, often in collaboration with François Perrot of the French Atomic Energy commission. The neutral-pseudo atom model (NPA) for warm dense matter is one of their main contributions of great practical value where finite-temperature density functional theory has been used to formulate a rigorous quantum mechanical approach to hot ionized matter. Subsequently, the construction of the classical-map scheme for quantum systems is a ground-breaking work, leading to the formulation of the classical-map hyper-netted chain method (CHNC). This method has led to a new approach for the evaluation of properties of Fermi liquids and warm-dense matter.

His previous work on the density-functional theory of dense plasmas is now well-established in the NPA model. It has led to the development of methods for the first-principles evaluation of the equation of state, and the transport properties of dense plasmas. His contributions to the energy-relaxation of hot electrons in semiconductors and also in plasmas,have presented a new direction in the theory of non-equilibrium states of two-temperature charged fluids. His paper elucidating the unusual thermal conductivity of clathrates still attracts many citations. His contributions to surface science (e.g. reconstruction of the sulphur-passivated InP surface), nanotechnology, phonons in semiconductor structures, quasi-periodic systems etc., are well known and are contained in over 200 research publications. Dharma-wardana currently serves as a principal research scientist at the National Research Council of Canada, and is a professor of theoretical physics at the Université de Montréal. His most recent book on physics is entitled *A Physicist's View of Matter and Mind*, published in 2013 by World Scientific.

### LEWIS, Laurent J.

Professeur titulaire

- Numerical simulation
- Materials science
- Computational techniques, simulation
- Amorphous semiconductors, metals, and alloys
- Disordered solids
- Glasses
- Laser-beam impact phenomena
- Molecular dynamics and particle methods
- Nanoscale materials and structures: fabrication and characterization
- Thermal properties of small particles, nanocrystals, nanotubes and other related systems

My research program examines the general theme of computational physics of materials. We use powerful computers to probe the structural and other behaviour and properties of materials, and the "structure-function" relationship. Our preferred approach is molecular dynamics, which involves integrating the equations of motion of a system of atoms under the effect of forces from "potentials"; they may be generic (Lennard-Jones, for instance), empirical or semi-empirical, or even *ab initio*. The size of the systems depends on the potential used and varies from tens or hundreds of atoms to several million.

We study a vast range of problems, but we are particularly interested in the following ones, just as an example: (i) laser ablation and laser-material interactions; in this case we are trying to understand how matter reacts to powerful, short laser pulses - ejection mechanisms, structural modifications of the target, properties of the ablation plume, etc. (ii) disordered, amorphous or vitreous materials; in this field, we are trying to understand the short-, medium- and long-term structure of materials like amorphous silicon, metallic glass, etc. (iii) thermal properties of nanoscopic materials; we are trying to determine how heat dissipates near nanometric structures and how it moves in molecular junctions between nanoparticles, in particular.