Theoretical Studies of Glasses

[00:81006 . drabold]本基金支持一位对硫系玻璃电子特性的理论研究感兴趣的职业中期PI的工作。这些是玻璃，含有纯形式的硒和硫，也含有它们的合金。在第一个项目中，计算了光学间隙附近的电子状态，包括晶格动力学效应和使用最先进的方法。这些态对这些材料的输运、掺杂和光学特性至关重要。第二个项目研究光引起的结构变化。实验表明，这种光诱导的结构变化可能是空间非局域的，并导致非热光熔化和巨大光膨胀等戏剧性现象。将对这些玻璃模型进行研究，使用Mousseau和Barkema的激活松弛技术，结合快速的近似从头算方法。将对选定的玻璃的表面状态进行有限的研究，这既是为了它们的基本兴趣，也是为了光引起的结构变化，特别是光熔化。最后，还有相关的方法方面，如非绝热动力学。这些研究将涉及明智地应用技术，从最简单的经验势到密度泛函方法，在具有广义梯度修正的局部自旋密度近似中。这项资助支持一位职业生涯中期的私家侦探的工作，他对硫系眼镜的光化学效应很感兴趣。该课题是理解太阳能电池运行效率的关键，因为如果它们的材料发生实质性的结构变化，作为其作为光电设备运行的结果，那么了解这种变化是如何发生的，可能会提出提高电池寿命的方法。此外，由于所涉及的物理是微妙的，并且其效果已经超出了传统方法和近似的范围，因此该主题具有根本的重要性

0081006DraboldThis grant supports the work of a mid-career PI, interested in a theoretical study of the electronic properties of chalcogenide glasses. These are glasses, which involve selenium and sulfur, in their pure form and also alloys involving them. There are three research projects: In the first one, there is a calculation of the electron states near the optical gap, including lattice dynamics effects and using state of the art methods. These states are of critical importance in the transport, doping and optical characteristics of these materials. The second project studies light induced structural changes. Experiments show that such light induced structural changes may be spatially non-local and lead to dramatic phenomena such as athermal photo-melting and giant photo-expansion. There will be a study of models of these glasses, using the activation-relaxation technique of Mousseau and Barkema, in conjunction with fast, approximate ab initio methods. A limited study of the surface states of selected glasses will be performed, both for their fundamental interest as well as for light-induced structural changes, especially photomelting. Finally, there are the associated methodological aspects, e. g. non-adiabatic dynamics. These studies will involve a judicious application of techniques ranging from the simplest empirical potentials to density functional methods in the local spin density approximations with generalized gradient corrections.%%%This grant supports the work of a mid-career PI who is intrigued by the photomechanical effects in chalcogenide glasses. The subject is key to an understanding of the solar cells' operating efficiency in that if their are substantial structural changes in the material, as a result of its operation as a photoelectric device, then an understanding of how that happens might suggest ways of improving the battery lifetimes. Additionally the subject is of fundamental importance since the physics involved is subtle and the effects have been beyond the reach of conventional methods and approximations.***