Polymorphic phase transition mechanism of compressed coesite.

Silicon dioxide is one of the most abundant natural compounds. Polymorphs of SiO₂ and their phase transitions have long been a focus of great interest and intense theoretical and experimental pursuits. Here, compressing single-crystal coesite SiO₂ under hydrostatic pressures of 26-53 GPa at room temperature, we discover a new polymorphic phase transition mechanism of coesite to post-stishovite, by means of single-crystal synchrotron X-ray diffraction experiment and first-principles computational modelling.

First-order liquid-liquid phase transition in cerium.

We report the first experimental observation of a liquid-liquid phase transition in the monatomic liquid metal cerium, by means of in situ high-pressure high-temperature x-ray diffraction experiments. At 13 GPa, upon increasing temperature from 1550 to 1900 K high-density liquid transforms to a low-density liquid, with a density difference of 14%. Theoretic models based on ab initio calculations are built to investigate the observed phase behavior of the liquids at various pressures.

Uniform illumination and rigorous electromagnetic simulations applied to CMOS image sensors.

This paper describes a new methodology we have developed for the optical simulation of CMOS image sensors. Finite Difference Time Domain (FDTD) software is used to simulate light propagation and diffraction effects throughout the stack of dielectrics layers. With the use of an incoherent summation of plane wave sources and Bloch Periodic Boundary Conditions, this new methodology allows not only the rigorous simulation of a diffuse-like source which reproduces real conditions, but also an important gain of simulation efficiency for 2D or 3D electromagnetic simulations.