摘要:
基于密度泛函理论平面波方法研究了IVB族过渡金属氮化物TiN, ZrN, HfN的电子结构、弹性性质和光学性质.研究表明, IVB族过渡金属氮化物晶格的电子结构分别体现了共价性、离子性和金属性,且基态下体系呈金属性.各晶格在坐标基矢方向上的杨氏模量的数值与体对角线方向上的差距明显,体现出典型的弹性性质各向异性,这导致了实验研究在制备其薄膜时不可避免地产生晶格畸变与微裂纹.伴随着态密度中赝隙的红移, TiN, ZrN, HfN的金属性依次增强,使得材料在力学性能方面脆性减弱,单晶的各向异性程度提升,以及光学性质方面电子跃迁机理由带内跃迁到带间跃迁转变所需入射光子能量的蓝移和光谱选择性能的下降.因此,通过降低IVB族过渡金属氮化物中自由电子的组分以加强材料的共价性,有利于提高材料弹性性质的各向同性,改善材料的光谱选择性能.
Abstract:
@@@@The elastic and optical properties of face-centered cubic IVB group transition metal nitrides such as TiN, ZrN, and HfN are calculated using the plane wave pseudopotential method based on first-principle density function theory. Electronic property is a combination of covalent, ionic, and metallic property. And band structures of these compounds show metallicities in the ground state. The obvious numerical differences between E[100] and E[111] indicate elastic anisotropy. The phenomena result in lattice distortions and microcracks in these metal nitride films. With red shift of pseudogap, the metallic properties of TiN, ZrN, and HfN are improved in turn. And the elastic and optical properties change with metallic properties improving: brittleness reduces, the degree of anisotropy increases, the critical energy between intraband and interband transitions increases, and the solar-optical selectivity decreases. So reducing the number of conduction electrons to strengthen covalency is an effective method to improve elastic isotropy and optical selectivity.
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