Jahangiri Soran, Mosey Nicholas J
Department of Chemistry, Queen's University, 90 Bader Lane, Kingston, ON K7M 0A9, Canada.
Phys Chem Chem Phys. 2017 Jan 18;19(3):1963-1974. doi: 10.1039/c6cp07968g.
Metal hydroxides are a class of layered materials that contain two-dimensional metal hydroxide layers that can be isolated to form layered nanostructures. In this work, density functional theory (DFT) and self-consistent-charge density-functional tight-binding (SCC-DFTB) methods have been used to investigate the properties of magnesium hydroxide and calcium hydroxide nanostructures. The properties of single layer and multi layer structures with up to 10 metal hydroxide sheets and nanoparticles containing more than 2000 atoms have been calculated and compared with the bulk properties of these systems. The accuracy of the DFT methods employed and SCC-DFTB parameters developed in this study were validated against available experimental data. The results of the calculations indicate that significant differences exist between the properties of the nanostructures and the corresponding bulk values. In particular, the interlayer binding energies, electronic band gaps, and spectroscopic features are size-dependent and tend to converge to the bulk values as the size of the nanosystem is increased. The calculated binding energies and shear moduli show that all nanostructures are mechanically stable, in agreement with the experimental reports; although, their stabilities may be affected by the presence of intercalated species. Energy decomposition analyses reveal that the intralayer interactions in the investigated systems are predominantly electrostatic in nature, while the interlayer interactions are dominated by dispersion and polarization components. The results presented here quantify various properties of magnesium hydroxide and calcium hydroxide nanostructures, and could be used to understand the properties of other nanosystems containing layers of metal hydroxides in their structure.
金属氢氧化物是一类层状材料，其包含二维金属氢氧化物层，这些层可以被分离以形成层状纳米结构。在这项工作中，密度泛函理论（DFT）和自洽电荷密度泛函紧束缚（SCC-DFTB）方法已被用于研究氢氧化镁和氢氧化钙纳米结构的性质。已计算了具有多达10个金属氢氧化物片层的单层和多层结构以及包含超过2000个原子的纳米颗粒的性质，并与这些体系的体相性质进行了比较。本研究中采用的DFT方法的准确性和开发的SCC-DFTB参数已根据现有实验数据进行了验证。计算结果表明，纳米结构的性质与相应的体相值之间存在显著差异。特别是，层间结合能、电子带隙和光谱特征与尺寸有关，并且随着纳米体系尺寸的增加趋向于收敛到体相值。计算得到的结合能和剪切模量表明，所有纳米结构在力学上都是稳定的，这与实验报告一致；尽管它们的稳定性可能会受到插层物种存在的影响。能量分解分析表明，所研究体系中的层内相互作用本质上主要是静电相互作用，而层间相互作用则由色散和极化分量主导。这里给出的结果量化了氢氧化镁和氢氧化钙纳米结构的各种性质，并可用于理解其他结构中包含金属氢氧化物层的纳米体系的性质。
