Laurent Bellaiche joined our department in January 1999. He received physics BS. MS.and PhD degrees Summa Cum Laude at the University of Paris VI. His dissertation title was "Theoretical and experimental study of different aspects of the electronic density in BN, LiH and Be single crystals."

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He became Research Associate at the University of Paris XI in August 1994, where he provided theoretical support to experimental groups on surface reconstruction and high pressure effects in semiconductors. In September 1995, he was chosen out of 200 candidates to join the National Renewable Energy Laboratory in Golden, Colorado, where he performed calculations on semiconductor alloys. Two years later, Dr. Bellaiche transferred to the Department of Physics and Astronomy at Rutgers University, where he did theoretical investigations of ferroelectric systems. He taught undergraduate and graduate courses at both Paris and Rutgers Universities. He received various academic honors, including four fellowships for materials science studies, and research and teaching awards from the French government and from different Paris universities, and co-authored over 20 journal articles, including 3 in Physical Review Letters and 3 in Applied Physics Letters during the past two years. He gave invited presentations at APS meetings, about his semiconductor alloys studies at the 1998 March Meeting and about his ferroelectric systems work at the 1999 Atlanta Centennial Meeting, and four other invited talks.

Dr Bellaiche's primary research interest is the prediction, design, and optimization of materials properties. To reach that goal, he uses and develops state-of-the-art computational and simulation methods. His current research program is divided into three activities: ferroelectric systems, semiconductor materials, and high pressure physics.

The ferroelectric systems have the ability to swell or shrink when electricity flows through them, as well as to give off electricity themselves when compressed or pulled apart. Engineers have exploited this trait for decades to convert mechanical energy to electricity and back again in applications ranging from phonograph needles to telephone speakers. The versatile family of ferroelectric systems has recently gained some even more gifted members which display an effect 10 times greater than that of the current family members. These new members could usher in a new generation of devices that would improve everything from the resolution of ultrasound machines to the range of sonar listening devices. One of Dr Bellaiche's goals is to predict the properties of ferroelectric systems, and to identify the microscopic effects responsible for their anomalous behaviors.

In semiconductor systems, he is especially interested in the effects of surfaces and alloying on structural, optical and electronic properties. He focuses on the microscopic understanding of nitride semiconductor alloys. These systems promise to greatly improve the high-temperature performance of the laser diodes used in optical-fiber communications. They are also of fundamental interest since they exhibit very unusual semiconductor alloy features, including an anomalous composition- and pressure-dependence of the band gap. Gaining a broad atomic understanding of these nitride alloys may lead us to revisit common beliefs about semiconductor properties, and to an optimization of device performance.

In his high-pressure physics research, Dr. Ballaiche studies pretransitional effects, i.e. effects in a crystallographic structure just before it undergoes a phase transition to another structure. Although a systematic understanding of the crystal structure of the ground state and of the high-pressure phases in terms of ionicity and atomic instabilities has been achieved over the past 2-3 decades, the existence of pretransitional effects is not at all understood. Little is known about their microscopic signatures. How are electronic properties affected by these effects? What are their consequences on ionicity, bond angles, and atomic distances? Understanding the cause(s) and consequences of pretransitional effects is of great fundamental interest, and will significantly improve our current knowledge of high pressure phenomena.

Dr Bellaiche's research interests are shared by several members of our department, e.g. Paul Thibado for semiconductors, Lin Oliver for ferroelectric systems and high pressure physics, and Greg Salamo for ferroelectric systems and semiconductors. These common interests should generate fruitful interactions and collaborations.

One of Dr Bellaiche's main goals is to efficiently train undergraduate and graduate students. He intends to do that by leading them to a deep understanding of various fundamental and technological problems, and by showing them how these two aspects of science are related at a microscopic scale. Learning computer skills will also enhance students' ability to compete on the job market.