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Electronic and vibrational properties of vanadium-carbide nanowires

机译：碳化钒纳米线的电子和振动特性

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摘要

We have made an effort to understand the properties of transition metal carbide nanowires (NWs) and studied vanadium-carbide (VC) nanowires as a specific case. Different structures have been considered and their electronic and vibrational properties studied employing density functional theory. The effect of dimensionality is very well brought forth by these NWs, narrow/thinner structures have clear preference for magnetic state with sizeable magnetic moment at the V sites. As the thickness/width increases, the margin decreases and the magnetic moment disappears altogether for structures like square and rectangular NWs. The cohesive energy per atom increases with the increase in lateral dimensions of the NW, and it is about 88% of the bulk value for the rectangular NW, while it is only 50% for the linear chain. All the wires are conducting in nature, with the linear and zigzag wires having half-metallic character. Our calculations show that the V atoms decide the electronic and magnetic properties in these while compressibility, a mechanical property, is governed by the C atoms. The electron localization function beautifully illustrates the closeness of thicker/wider NWs to the bulk. It also reveals that electrons are highly localized around C atoms; however, the amount of charge transferred depends strongly on the structure of wire. The optical properties unfurl the impact of different spatial expanse in the cross section of NW in a nice way, e.g., ε2xx > ε2yy (ε2 is imaginary part of dielectric function) for all those with a larger expanse along X compared to Y and vice-versa. Thicker nanowires seem to be more suitable for optical applications. Site-resolved phonon density of states shows that presence of C atoms is responsible for high frequency branches. The heat capacity variation for various structures closely follows the magnitude of respective phonon density of states.
机译：我们已努力了解过渡金属碳化物纳米线（NWs）的性能，并研究了碳化钒（VC）纳米线的具体情况。已经考虑了不同的结构，并使用密度泛函理论研究了它们的电子和振动特性。这些NW很好地带来了尺寸的影响，窄/薄结构明显倾向于在V位置具有较大磁矩的磁态。随着厚度/宽度的增加，对于方形和矩形NW等结构，余量减小，磁矩完全消失。每个原子的内聚能随着NW的横向尺寸的增加而增加，大约是矩形NW体积值的88％，而对于线性链只有50％。所有的导线本质上都是导电的，线性和之字形导线具有半金属特性。我们的计算表明，V原子决定了其中的电子和磁性，而可压缩性（机械性能）则受C原子支配。电子定位功能很好地说明了较厚/较宽的NW与整体的接近程度。它也揭示了电子高度集中在C原子周围。但是，转移的电荷量很大程度上取决于导线的结构。光学特性很好地克服了NW横截面中不同空间扩展的影响，例如，对于所有在X方向上具有比Y更大的沿X方向扩展的那些，ε2xx>ε2yy（ε2是介电函数的虚部），反之，反之亦然。较粗的纳米线似乎更适合光学应用。位置分辨声子的状态密度表明，C原子的存在是高频分支的原因。各种结构的热容变化紧密地遵循各个声子密度的大小。

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  • 来源
    《Journal of Applied Physics》 |2012年第6期|p.1-9|共9页
  • 作者

    Singh Poorva; Nautiyal Tashi; Auluck Sushil;

  • 作者单位

    Department of Physics, Indian Institute of Technology Roorkee, Roorkee 247667, India;

  • 收录信息 美国《科学引文索引》(SCI);美国《工程索引》(EI);美国《生物学医学文摘》(MEDLINE);
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