arXiv 0801.47782008-01-30cond-mat.mtrl-scicond-mat.other

Off-center impurities in alkali halides: reorientation, electric polarization and binding to F center. V. Temperature-dependent electrostatic polarizabilities

Mladen Georgiev

备注：: 6 pages including 1 figure, all pdf format

英文摘要：

We derive and discuss expressions for the temperature-dependent electrostatic polarizabilities of off-center ions holding good under various experimental conditions. At low temperatures and electric-field strengths, all of them reasonably reduce to values characteristic of phonon-coupled two-level systems. Prospects for further studies of the dispersive coupling are also considered.

机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。

阅读原文

阅读 PDF ↗

arXiv 页面 ↗HTML 原文 ↗

本文内容

英文摘要相关论文

机构、总结、中文摘要均由AI分析而来，可能存在错误，请以论文正文为准。

继续探索

相关论文

Off-center impurity in alkali halides: reorientation, electric polarization and pairing to F center. I. Basic equations

Extending earlier work on a vibronic theory of the FA centers in alkali halides, the reorientation is now considered of an off-center Li+ impurity, either isolated or near an F center. We derive analytically periodic potential energy barriers between metastable reorientational off-center sites, the barriers hindering the impurity rotation around the normal lattice site. Applying to a specific model, electron-vibrational mode coupling constants are calculated up to 3rd order of the expansion of the coupling energy in the T1u mode coordinates. The 3rd order coupling brings about additional renor…

2007-09-12cond-mat.mtrl-scicond-mat.other

Influence of the Halide Ion on the A Site Dynamics in FAPbX3 (X = Br and Cl)

The optoelectronic properties and ultimately photovoltaic performance of hybrid lead halide perovskites, is inherently related to the dynamics of the organic cations. Here we report on the dynamics of the formamidinium (FA) cation in FAPbX3 perovskites for chloride and bromide varieties, as studied by neutron spectroscopy. Elastic fixed window scan measurements showed the onset of reorientational motion of FA cations in FAPbCl3 to occur at a considerably higher temperature compared to that in FAPbBr3. In addition, we observed two distinct dynamical transitions only in the chloride system, sugg…

2022-02-09cond-mat.mtrl-scicond-mat.other

Reaction rate approach to dipolar relaxation in alkali halides: Adiabaticity versus classical, activated-tunneling, and quantal dipoles

This paper is aimed at presenting a simple vibronic model for describing the dipolar reorientation in crystals by means of reaction rate theory. The Hamiltonian of an isolated dipole is simplified so as to render the problem solvable. Depending on the crossover splitting the dipoles may reorientate adiabatically with a high electron-transfer expectancy or exhibit low reorientation rates due to low expectancy. An important quantity to distinguish between adiabatic dipoles behaving classically and ones reorientating by means of quantum-mechanical tunneling is Christov's characteristic temperatur…

2007-03-22cond-mat.mtrl-sci

Ground state properties of heavy alkali halides

We extend previous work on alkali halides by calculations for the heavy-atom species RbF, RbCl, LiBr, NaBr, KBr, RbBr, LiI, NaI, KI, and RbI. Relativistic effects are included by means of energy-consistent pseudopotentials, correlations are treated at the coupled-cluster level. A striking deficiency of the Hartree-Fock approach are lattice constants deviating by up to 7.5 % from experimental values which is reduced to a maximum error of 2.4 % by taking into account electron correlation. Besides, we provide ab-initio data for in-crystal polarizabilities and van der Waals coefficients.

1998-01-06cond-mat.mtrl-sci

Dynamic disorder, phonon lifetimes, and the assignment of modes to the vibrational spectra of methylammonium lead halide perovskites

We present Raman and terahertz absorbance spectra of methylammonium lead halide single crystals (MAPbX3, X = I, Br, Cl) at temperatures between 80 and 370 K. These results show good agreement with density-functional-theory phonon calculations.1 Comparison of experimental spectra and calculated vibrational modes enables confident assignment of most of the vibrational features between 50 and 3500 cm-1. Reorientation of the methylammonium cations, unlocked in their cavities at the orthorhombic-to-tetragonal phase transition, plays a key role in shaping the vibrational spectra of the different com…

2016-06-06cond-mat.mtrl-sciphysics.chem-ph