We use large-scale simulations to investigate the dynamic fracture of silica and sodium-silicate glasses under uniaxial tension. The stress-strain curves demonstrate that glass is brittle whereas rich in Na show pronounced ductility. A strong composition dependence also seen crack velocity which, for strain rate considered, on order 1800 m/s with low concentration decreases 650 if high. find du...

The modern STEM is capable of providing a wealth of information, but without fast, efficient detectors that wealth would be lost. Over the last few years, EELS systems have become faster, more efficient and capable of acquiring large energy and dynamic ranges while EDS detectors have greatly increased collection angles and counting rates. These advances would be meaningless without the improved...

We have theoretically studied the space-time entangled biphoton state generated from a two-level atomic system. In the photon counting measurement, the two-photon coincidence counting rate is a damped oscillation. The oscillation period is determined by the effective Rabi frequency and the damping rate is determined by the linewidth of the inhomogeneous-broadened ground state and the dipole dep...

We study a four-level atomic scheme interacting with four lasers in a closed-loop configuration with a L ~diamond! geometry. We investigate the influence of the laser phases on the steady state. We show that, depending on the phases and the decay characteristic, the system can exhibit a variety of behaviors, including population inversion and complete depletion of an atomic state. We explain th...

Recent work on using atomic-level simulation methods to study the ferroelectric properties of oxide materials is reviewed. In particular, it is illustrated how such methods can provide insights into the physical properties of a wide range of ferroelectric oxide materials inaccessible by other means. Approaches for further improvements in materials fidelity and increased range of applicability a...

Twenty-two years after their discovery as ribozymes, the self-splicing group I introns are finally disclosing their architecture at the atomic level. The crystal structures of three group I introns solved at moderately high resolution (3.1-3.8A) reveal a remarkably conserved catalytic core bound to the metal ions required for activity. The structure of the core is stabilized by an intron-specif...