Homogenization scheme for brittle intergranular decohesion in polycrystalline aggregates

International audienc

Modeling IR spectra of CO2 isotopologues and CH4 trapped In type I clathrate

To test the hypothesis of atmospheric carbon dioxide or methane storage in metastable clathrate, a theoretical formalism is developed to model and simulate the spectra of the CO2 or CH4 molecule trapped in clathrates. 12-6 Lennard-Jones atomatom potentials are used to account for short and long range interactions between the atoms of the trapped molecules and atoms of H2O molecules of the cage. Effective electric charges are used for electrostatic interactions with H2O molecules. The calculations were performed on clathrates of type I, with a small and a large cage to determine equilibrium configurations for both CO2 and CH4 and vibrational shifts were determined for CO2 in an undistorted trapping nano-cage

Analysis of the hysteretic behaviour of 3D spin crossover compounds by using an ising-like model

In this contribution, we use a recently developed Monte Carlo technique to investigate the impact of ferro-, antiferromagnetic interactions for different thermodynamic parameters in a three-dimensional Ising-like model. We present the role of temperature and pressure on the first-order phase-transition between a low-spin and a high-spin state and identify different response curves. The analysis of one- and two-step spin-crossover behaviour has been performed by using a self-consistent approach, because it is known that for a system with both short- and long-range interactions, the Hamiltonian does not have an exact solution. However, by constructing the distributions of the states with Monte Carlo entropic sampling and by taking into account the temperature degeneracy dependence between low-spin and high-spin states, we could solve the Hamiltonian. We provide herein a systematic comparison to our previous experimental works and as part of our continuous interest in spin crossover nanosystems, we present a size effect study. The effects of size, pressure and interactions on 3D spin crossover systems within the framework of an Ising-like model are discussed. Copyright © 2013 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Experimental analysis of ¹³CO₂ infrared stimulated

Vibrational stimulated emissions of CO₂ trapped in low temperature argon matrices have been found experimentally not only in the 16 mm region (v₂ manifold) but also at 10 mm (v₃ - v₁ transition) in the double trapping site of concentrated samples. A detailed experimental description of these emissions is reported, including spectral analysis, time-resolved studies, laser energy dependence, and concentration and temperature effects. The characteristics of the emissions are discussed, giving some insight into the nonradiative intramolecular V–V transfers from the laser excited level v₃=1 towards the v₂ manifold, and inside this manifold