基于无机铅卤钙钛矿的第一性原理分析

运用Material Studio 7.0软件构建模型,对不同卤化物所构成的无机铅卤钙钛矿进行了第一性原理分析,选用了点群结构为Pm3m的CsPbX_3(X=Cl,Br,I)立方晶胞,并在此基础上优化分析了带隙结构和态密度.通过调整不同的交换泛函得到了同一CsPbBr_3单胞优化后的不同的带隙和体模量.并对同一泛函PBE下CsPbCl_3、CsPbBr_3、CsPbI_3的带隙大小、态密度等结果进行了分析,结果显示,随着晶格参数从Cl到I变大,钙钛矿的体模量和电子带隙会变小,离子性也得到了增强.     

Biphasic behavior of energy in a stepped chain

The impact energy decay in a step-up chain containing two sections is numerically studied.There is a marked biphasic behavior of energy decay in the first section.Two sections close to the interface are in compression state.The degree of compression of the first section first decreases and becomes weakest at "crossing" time of biphasic behavior of energy,then increases.The further calculations provide the dependence of the character time on mass ratio(m1/m2),where m1 and m2are the particle mass in the first and second section respectively.The bigger the α(α = [(? m_1-m_2)/(? m_1+ m_2)]~2 with? = 1.345),the bigger the energy ratio is.The multipulse structure restricts the transport of energy.