QSG: People: Aaron Puzder

	Contact Information
	NAME	Aaron Puzder
	PHONE	(925) 423-1756
	FAX	(925) 422-6594
	E-MAIL	puzder1@.llnl.gov
	ADDRESS	Lawrence Livermore National Lab 7000 East Avenue, L-415 Livermore, CA 94550

Research Interests

My research interests and objectives has focused on the electronic structure of condensed matter, primarily on finite systems. Calculations are performed using first-principles methods without adjustable parameters. The purpose of these studies is to provide unambiguous expalnations for various interesting phenomena observed in clusters, surfaces, and atoms, as well as to make reliable predictions of new properties from microscopic quantum theories, specifically density functional theory (DFT) and quantum Monte Carlo (QMC).

My theoretical efforts can be broken into two broad categories 1) optical, electronic, and structural properties of semi-conductor nanoclusters and 2) new calculational methods for studying quantum mechanical systems. A detailed description follows:

I.) SURFACE CHEMISTRY OF SILICON NANOCLUSTERS - Quantum confinement dominates the optical gaps of silicon clusters in a narrow size regime a few nanometers in diameter. However, different passivants such as hydrogen, oxygen, fluorine, a hydroxyl group, etc. can change the properties as well, either the structural stability of the cluster, the optical gap, or the strength of transition. Current research investigates all these properties.

II.) CONDUCTION BAND SHIFT IN GERMANIUM NANOCLUSTERS - The smallest germanium cluster and the largest have smaller optical gaps than silicon clusters the same size. Yet, in between, the germanium gap is larger. Using QMC, we look at this effect in detail as well as ascertain the exact "crossover".

III.) EMISSION IN SILICON NANOCLUSTERS - The wavelength of light which a silicon nanocluster absorbs is different from that which it emits. This "Stokes shift" phenomena is studied in detail using DFT to relax a silicon nanocluster in its excited state (simulating light absorption), and then using QMC to see the resulting change. The use of such accurate atomistic models can hopefully explain the wide discrepency in experiments involving the difference between absorbed and emitted light in any given cluster.

IV.) ELECTRONIC STRUCTURE OF CADMIUM SELENIDE (CdSe) CLUSTERS - Unlike silicon, CdSe are understood and predictable as to the light they absorb and emit. Also unlike silicon, CdSe is much more difficult to theoretically model accurately because of the extra "d" shell of electrons. Current research involves rigorous computational calculations on the elctronic structure of CdSe taking into accout all s, p, and d electrons.

V.) THEORETICAL DEVELOPMENT IN DFT - Using highly accurate variational trial wavefunctions, we have modeled various quantities of interest in DFT including the pair-correlation function, the exchange-correlation hole, and the exchange-correlation energy functional. The results have led to new insights and approximate models of such functionals used in DFT, including weighted spin density functionals.

People in the Quantum Simulations Group

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Date last modified: 01/28/02
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