Bonding and classification of nanolayered ternaray carbides
Bonding and classification of nanolayered ternaray carbides
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DOI：
10.1103/physrevb.70.092102
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发表时间：
2004-09
期刊：
影响因子：
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通讯作者：
Zhimei Sun;D. Music;R. Ahuja;Saying Li;J. Schneider
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文献类型：
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作者：
Zhimei Sun;D. Music;R. Ahuja;Saying Li;J. Schneider
本论文采用基于密度泛函理论 (DFT) 的从头计算方法对块体材料进行了理论研究。5f-二氧化物、ABO3 钙钛矿和 ABO4 化合物的晶体结构相变和相稳定性已得到广泛研究。静态总能量计算、弹性稳定性和动态稳定性（声子计算）标准等不同方法已用于确定相位稳定性。作为一个特例，研究了固体 Xe 的晶格动力学随压力的变化。计算了浓度 x=0、0.25、0.5 和 1.0 的太阳能电池系统 CuIn1-xGaxSe2 以及 C60、PbWO4 和 δ-AlOOH 的介电函数和光学常数。吸收系数提供有关最佳太阳能转换效率的信息。我们已经导出了许多化合物的吸收系数。对计算的介电函数和吸收系数与实验的介电函数和吸收系数进行了比较。本文的主要部分集中于纳米层三元化合物M N+1AXN (MAX)，其中N = 1、2或3，M是早期过渡金属，A是A族（主要是IIIA和IVA）元素，X是C和/或N。这些三元碳化物和氮化物结合了金属和陶瓷的不寻常性质。它们表现出高硬度，但具有完全可逆的塑性，并且热电势可以忽略不计。这些优异的性能使 MAX 相成为另一种具有多种技术应用的新型材料。我们的工作对 MAX 相的电子、键合、弹性和光学特性进行了系统研究。一种新的MAX相——Ti4SiC3，经计算是稳定的，同时也被实验人员合成。还对 Ti-Si-C 系统的 (0001) 表面进行了表面能计算。论文详细阐述了MAX相的电子结构与材料性能之间的一般关系。
This thesis presents a theoretical study of bulk materials using ab initio methods based on the density functional theory (DFT).Crystallographic structural phase transformations and phase stability for 5f-dioxides, ABO3 perovskites, and ABO4 compounds have been extensively studied. Different approaches such as static total energy calculations, elastic stability and dynamical stability (phonon calculations) criteria have been used to determine the phase stability. As a special case, the lattice dynamics of solid Xe has been studied as a function of pressure.Dielectric functions and optical constants have been calculated for solar energy cell system CuIn1-xGaxSe2 with concentrations x=0, 0.25, 0.5 and 1.0 as well as for C60, PbWO4 and δ-AlOOH. The absorption coefficient provides information about the optimum solar energy conversion efficiency. We have derived absorption coefficients for a number of compounds. Comparisons between the calculated and experimental dielectric functions and absorption coefficients have been made.The main part of this thesis focuses on the nanolayered ternary compounds M N+1AXN (MAX), where N = 1, 2 or 3, M is an early transition metal, A is an A-group (mostly IIIA and IVA) element, and X is either C and/or N. These ternary carbides and nitrides combine unusual properties of both metals and ceramics. They exhibit high hardness, but fully reversible plasticity, and negligible thermoelectric power. These excellent properties make the MAX phases another new class of materials with versatile technological applications. Our work presents a systematic study of the electronic, bonding, elastic and optical properties of the MAX phases. A new MAX phase-Ti4SiC3, is calculated to be stable, and at the same time also been synthesized by experimentalists. Surface energy calculations have also been performed for the (0001) surface of the Ti-Si-C system. The general relations between the electronic structure and materials properties of the MAX phases have been elaborated in the thesis.