基于从头计算分子动力学模拟的CH $_3$ NH $_3$ PbI $_3$钙钛矿的热效应
Thermal effects on CH$_3$NH$_3$PbI$_3$ perovskite from ab-initio molecular dynamics simulations
摘要：
基于密度泛函理论计算的力，对CH $_3$ NH $_3$ PbI $_3$进行了分子动力学模拟研究.在具有8个和27个单位单元的模型系统上进行模拟，并且在每种情况下总模拟时间为40 ps。有限尺寸效应的分析，特别是有机组分的流动性，表明较小的系统是通过远程静电相互作用的相关。在更大的系统中，这种有限大小的伪影被放松，产生对甲基铵分子的各向异性旋转行为的更可靠的描述。分析了热效应对系统光学特性的影响。HOMO-LUMO能隙围绕其中心值波动，标准偏差约为0.1 eV。在整个模拟轨迹中，费米能级始终位于I原子的$p$轨道上，最低虚态始终位于Pb原子的$p$轨道上.
英文摘要：
We present a molecular dynamics simulation study of CH$_3$NH$_3$PbI$_3$ based on forces calculated from density functional theory. The simulation were performed on model systems having 8 and 27 unit cells, and for a total simulation time of 40 ps in each case. Analysis of the finite size effects, in particular the mobility of the organic component, suggests that the smaller system is over correlated through the long range electrostatic interaction. In the larger system this finite size artifact is relaxed producing a more reliable description of the anisotropic rotational behavior of the methyl ammonium molecules. The thermal effects on the optical properties of the system were also analyzed. The HOMO-LUMO energy gap fluctuates around its central value with a standard deviation of approximately 0.1 eV. The projected density of states consistently place the Fermi level on the $p$ orbitals of the I atoms, and the lowest virtual state on $p$ orbitals of the Pb atoms throughout the whole simulation trajectory.
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