...
  • 主题
高级搜索  >
历史搜索 清空历史
首页> 外文期刊>The journal of physical chemistry, A. Molecules, spectroscopy, kinetics, environment, & general theory >Plane-wave density functional theory study on the structural and energetic properties of cation-disordered Mg-Al layered double hydroxides
【24h】

Plane-wave density functional theory study on the structural and energetic properties of cation-disordered Mg-Al layered double hydroxides

机译：阳离子无序Mg-Al层状双氢氧化物的结构和能量性质的平面波密度泛函理论研究

获取原文
获取原文并翻译 | 示例
           
页面导航
  • 摘要
  • 著录项
  • 相似文献
  • 相关主题

摘要

Periodic solid models have been employed to investigate the structural and energetic properties of cation-disordered Mg-Al layered double hydroxides (LDHs), including composition, ordering, and stacking pattern of layers. The geometry, lattice energy and density of states (DOS) of the periodic models were computed using the plane-wave pseudopotential implementation of density functional theory (DFT) with the virtual crystal approximation (VCA). The calculation results for the MgAl-Cl-LDH model show that a pure LDH phase is difficult to sustain when the Mg/Al ratio (R) is R ≥ 4. The stability of the cation-disordered MgAl-Cl-LDH unit cell increases upon increasing R, owing to the decrease in the number of Al(III)-O-Al(III) linkages in the LDH sheets. The highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) of MgAl-Cl-LDH receive contributions from the 3s and 3p orbitals of Mg and Al and the 2p orbitals of O and Cl, respectively, implying significant host-guest interactions. The increase of R leads to the decrease in electron density of 3s and 3p of metal cation and that of 2p in Cl. Consequently, the HOMO-LUMO energy gap as well as the systematical stability increase upon increasing R. From this point of view, it has been demonstrated that the cations distribute in an ordered arrangement with the absence of Al(III)-O-Al(III) linkages if R is in the low range (R = 2-3). It was also found that the 3R polytype is the most stable stacking pattern with the same Mg/Al ratio, owing to the fact that the conductive band energy levels decline with the increase of electron density of 3s and 3p of the metal cation in the 3R-stacking system. These findings agree well with the experimental results and provide a profound understanding of critical factors influencing the structure of LDHs, including metal composition and ordering, the stacking sequence, as well as the host-guest interactions.
机译：周期性固体模型已用于研究阳离子无序Mg-Al层状双氢氧化物（LDHs）的结构和能量性质，包括层的组成，有序性和堆积模式。周期模型的几何形状，晶格能量和状态密度（DOS）使用密度泛函理论（DFT）的平面波伪势实现与虚拟晶体近似（VCA）进行计算。 MgAl-Cl-LDH模型的计算结果表明，当Mg / Al比（R）为R≥4时，难以维持纯LDH相。阳离子无序MgAl-Cl-LDH晶胞的稳定性增加由于LDH片材中Al（III）-O-Al（III）键的数量减少，R增加。 MgAl-Cl-LDH的最高占据分子轨道（HOMO）和最低未占据分子轨道（LUMO）分别受到Mg和Al的3s和3p轨道以及O和Cl的2p轨道的贡献，这意味着重要的客体互动。 R的增加导致金属阳离子的3s和3p的电子密度降低，而Cl中的电子密度降低2p。因此，HOMO-LUMO的能隙以及系统稳定性随R的增加而增加。从这一观点出发，已证明阳离子在无Al（III）-O-Al（ III）如果R在低范围内（R = 2-3），则表示连锁。还发现3R多型是具有相同Mg / Al比的最稳定的堆积模式，这是由于随着3R中金属阳离子的3s和3p电子密度的增加，导带能级下降堆垛系统。这些发现与实验结果非常吻合，并提供了对影响LDHs结构的关键因素的深刻理解，包括金属成分和有序性，堆积顺序以及宿主与客体的相互作用。

著录项

相似文献

  • 外文文献
  • 中文文献
  • 专利
获取原文

客服邮箱：kefu@zhangqiaokeyan.com

京公网安备：11010802029741号 ICP备案号：京ICP备15016152号-6 六维联合信息科技 (北京) 有限公司©版权所有

  • 客服微信

  • 服务号