I have a broad range of interests in soft condensed matter physics and adjacent fields like statistical physics, physics of living systems and hard condensed matter. My particular focus is on the relationship between the geometric structure of a system and its mechanical response. Both biological and engineered systems often have some structure, such as networks of struts, particles jammed together or patterns of creases in thin sheets, that grant them flexibility and strength with a minimum of weight. These structures can lead to subtle and surprising mechanical response:

The Raman Group has two main thrusts.  The team utilizes sophisticated tools to cool atoms to temperatures less than one millionth of a degree above absolute zero. Using these tools, they explore topics ranging from superfluidity in Bose-Einstein condensates (BECs) to quantum antiferromagnetism in a spinor condensate.  In another effort the team partners with engineers to build cutting edge atomic quantum sensors on-chip that can one day be mass-produced.

Thadhani joined the faculty in the School of Materials Science and Engineering at Georgia Tech in September, 1992. His research focuses on studies of shock-induced physical, chemical, and mechanical changes for processing of novel materials and for probing the deformation and fracture response of metals, ceramics, polymers, and composites, subjected to high-rate impact loading conditions. He has developed state-of-the-art high-strain-rate laboratory which includes 80-mm and 7.62-mm diameter single-stage gas-guns, and a laser-accelerated thin-foil set-up, to perform impact experiments at velocities of 70 to 1200 m/s. The experiments employ time-resolved diagnostics to monitor shock-initiated events with nanosecond resolution employing piezoelectric and piezoresistive stress gauges, VISAR interferometry, Photonic-doppler-velocimetry, and high-speed digital imaging, combined with the ability to recover impacted materials for post-mortem microstructural characterization and determination of other properties. He has built computational capabilities employing continuum simulations for design of experiments and development and validation of constitutive equations, as well as for meso-scale discrete particle numerical analysis (using CTH and ALE3D codes) to determine the effects observed during shock compression of heterogeneous materials, using real microstructures.

During my research career I have observed “new” material systems develop and offer promise of wondrous device performance improvements over the current state of the art. Many of these promises have been kept, resulting in numerous new devices that could never have been dreamed of just a few short years ago. Other promises have not been fulfilled, due, in part, to a lack of understanding of the key limitations of these new material systems. Regardless of the material in question, one fact remains true: Without a detailed understanding of the electrical and optical interaction of electronic and photonic “particles” with the material and defect environment around them, novel device development is clearly impeded. It is not just a silicon world! Modern electronic/optoelectronic device designs (even silicon based devices) utilize many diverse materials, including mature dielectrics such as silicon dioxide/nitrides/oxynitrides, immature ferroelectric oxides, silicides, metal alloys, and new semiconductor compounds. Key to the continued progress of electronic devices is the continued development of a detailed understanding of the interaction of these materials and the defects and limitations inherent to each material system. It is my commitment to insure that new devices are continuously produced based on complex mixed family material systems.

Professor Yavari joined the School of Civil and Environmental Engineering at the Georgia Institute of Technology in January 2005. He received his B.S. in Civil Engineering from Sharif University of Technology, Tehran, Iran in 1997. He continued his studies at The George Washington University where he obtained an M.S. in Mechanical Engineering in 2000. He then moved to Pasadena, CA and obtained his Ph.D. in Mechanical Engineering (Applied Mechanics option with minor in Mathematics) from the California Institute of Technology in 2005. Professor Yavari is a Fellow of the Society of Engineering Science and a member of the American Academy of Mechanics.

Professor Yavari's interests are in developing systematic theories of discrete mechanics for crystalline solids with defects. Defects play a crucial role in determining the properties of materials. The development of atomistic methods including density functional theory, bond-order potentials and embedded atom potentials has enabled a detailed study of such defects. However, much of the work is numerical and often with ad hoc boundary/far-field conditions. Specifically, a systematic method for studying these discrete yet non-local problems is lacking. Design in small scales requires solving inverse problems and this is not possible with purely numerical techniques. From a mechanics point of view, defective crystals are modeled as discrete boundary-value problems. The challenging issues are extending the existing techniques from solid state physics for non-periodic systems, new developments in the theory of vector-valued partial difference equations, existence and uniqueness of solutions of discrete boundary-value problems and their symmetries, etc. The other efforts in this direction are understanding the geometric structure of discrete mechanics and its link with similar attempts in the physics and computational mechanics literatures and investigating the rigorous continuum limits of defective crystals

Zhu's research focuses on the modeling and simulation of mechanical behavior of materials at the nano- to macroscale. Some of the scientific questions he is working to answer include understanding how materials fail due to the combined mechanical and chemical effects, what are the atomistic mechanisms governing the brittle to ductile transition in crystals, why the introduction of nano-sized twins can significantly increase the rate sensitivity of nano-crystals, and how domain structures affect the reliability of ferroelectric ceramics and thin films. To address these problems, which involve multiple length and time scales, he has used a variety of modeling techniques, such as molecular dynamics simulation, reaction pathway sampling, and the inter-atomic potential finite-element method. The goal of his research is to make materials modeling predictive enough to help design new materials with improved performance and reliability.