Lubchenko, Vassiliy - University of Houston

个人简介

Ph.D., University of Illinois at Urbana-Champaign, 2002 M.S., Carnegie Mellon University, 1995 M.S., Moscow Institute of Physics and Technology, 1994

研究领域

My research interests include strongly disordered and non-equilibrium systems, with specific applications to materials science, molecular electronics, and biophysics. Our main focus is a self-consistent theory of structural and electronic excitations in amorphous materials. Several optical and electronic anomalies that are unique to semiconductor glasses have resisted systematic efforts for decades, including light induced ESR, midgap absorption, and insensitivity to conventional doping. Our findings show these anomalies are not a generic consequence of disorder, but, instead, result from the high structural degeneracy of glasses. An important component of our research is the prediction of the structure and glassforming ability of specific substances of interest in applications, a task currently inaccessible to computer technology. As part of the materials science project, we are developing first principles descriptions of inelastic deformation and fracture failure of glasses, amorphous solids in general, and other complex materials. Recent, critical developments in microscopic theories of glass formation are being used to describe visco-elastic properties of disordered media. Stress, corrosion, and radiation induced cracking are of basic and practical interest. As part of our biophysical research agenda, we are investigating the microscopics underlying recently discovered puzzling behaviors of concentrated protein solutions, in collaboration with Peter Vekilov's group. In conflict with traditional nucleation theories, long-living aggregates of mesoscopic size are found in such solutions. In addition to the basic significance of this problem, it is also important in the context of formation of various solid protein aggregates, such as crystals and protein fiber arrays implicated in sickle cell anemia.

近期论文

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"Microscopically based calculations of the free energy barrier and dynamic length scale in supercooled liquids: The comparative role of configurational entropy and elasticity Pyotr Rabochiy, Peter G. Wolynes, Vassiliy Lubchenko (Submitted on 15 Oct 2013) We compute the temperature-dependent barrier for alpha-relaxations in several liquids, without adjustable parameters, using experimentally determined elastic, structural, and calorimetric data. We employ the random first order transition(RFOT) theory, in which relaxation occurs via activated reconfigurations between distinct, aperiodic minima of the free energy. Two different approximations for the mismatch penalty between the distinct aperiodic states are compared, one due to Xia and Wolynes, which scales universally with temperature as for hard spheres, and one due to Rabochiy and Lubchenko, which employs measured elastic and structural data for individual substances. The agreement between the predictions and experiment is satisfactory, given the uncertainty in the measured experimental inputs. The explicitly computed barriers are used to calculate the glass transition temperature for each substance---a kinetic quantity---from the static input data alone. The temperature dependence of both the elastic and structural constants enters the temperature dependence of the barrier over an extended range to a degree that varies from substance to substance. The lowering of the configurational entropy, however, seems to be the dominant contributor to the barrier increase near the laboratory glass transition, consistent with previous experimental tests of the RFOT theory using the XW approximation. In addition, we compute the temperature dependence of the dynamical correlation length, also without using adjustable parameters. These agree well with experimental estimates obtained using the Berthier et al. procedure. Finally, we find the temperature dependence of the complexity of a rearranging region is consistent with the picture based on the RFOT theory but is in conflict with the assumptions of the Adam-Gibbs and ""shoving"" scenarios for the viscous slowing down in supercooled liquids."