First-Principles Semiclassical Initial Value Representation Molecular Dynamics

A method for carrying out semiclassical initial value representation calculations using first-principles molecular dynamics (FP-SC-IVR) is presented. This method can extract the full vibrational power spectrum of carbon dioxide from a single trajectory providing numerical results that agree with experiment even for Fermi resonant states. The computational demands of the method are comparable to those of classical single-trajectory calculations, while describing uniquely quantum features such as the zero-point energy and Fermi resonances. By propagating the nuclear degrees of freedom using first-principles Born-Oppenheimer molecular dynamics, the stability of the method presented is improved considerably when compared to dynamics carried out using fitted potential energy surfaces and numerical derivatives.Comment: 5 pages, 2 figures, made stylistic and clarity change

Suppressing molecular motions for enhanced room-temperature phosphorescence of metal-free organic materials

Metal-free organic phosphorescent materials are attractive alternatives to the predominantly used organometallic phosphors but are generally dimmer and are relatively rare, as, without heavy-metal atoms, spin-orbit coupling is less efficient and phosphorescence usually cannot compete with radiationless relaxation processes. Here we present a general design rule and a method to effectively reduce radiationless transitions and hence greatly enhance phosphorescence efficiency of metal-free organic materials in a variety of amorphous polymer matrices, based on the restriction of molecular motions in the proximity of embedded phosphors. Covalent cross-linking between phosphors and polymer matrices via Diels-Alder click chemistry is devised as a method. A sharp increase in phosphorescence quantum efficiency is observed in a variety of polymer matrices with this method, which is ca. two to five times higher than that of phosphor-doped polymer systems having no such covalent linkage.ope

Kinetic model for UV/H2O2 degradation of 8-methoxypsoralen

The influence of Н2О2 on the degradation of 8-methoxypsoralen (8-MOP) in water-ethanol solutions under the action of KrCl and XeBr excilamp radiation in a photoreactor is investigated. A kinematic model of photodegradation of the investigated molecule is constructed. In water-ethanol solutions the addition of Н2О2 altered the mechanism of decay of 8-MOP under the action of a KrCl excilamp in comparison with irradiation by a XeBr excilamp. This behavior is explained by the fact that the action of 283 nm radiation leads to accumulation of a stable photoproduct. In order to establish the toxicity of this product further research is needed