First-principles calculations of liquid CdTe at temperatures above and below the melting point
First-principles calculations of liquid CdTe at temperatures above and below the melting point
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高于和低于熔点温度下液态 CdTe 的第一性原理计算
DOI：
10.1103/physrevb.60.8640
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发表时间：
1999
期刊：
影响因子：
--
通讯作者：
J. Chelikowsky
中科院分区：
文献类型：
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作者：
V. Godlevsky;Manish Jain;J. Derby;J. Chelikowsky
在800K(过冷态)、1370K(接近熔化温度)和3000K(过热态)三个不同温度下，我们对CdTe进行了从头算分子动力学模拟。与实验一致，我们发现在熔化时，CdTe经历了$\mathrm{semiconducto}\stackrel{\ensuremath{\rightarrow}}{r}\mathrm{semiconductor}$相变。在液态下，CdTe仍保持其四面体的配位数为4。我们发现，加热远高于其熔点会导致结构发生实质性的变化，转变为更紧密堆积的原子结构。过热相的配位数为6，直流电导率比熔融温度大一个数量级。随着有限带隙的消失，这表明在高于熔点的温度下，Cd Te体系发生了逐渐的$\mathrm{semiconducto}\stackrel{\ensuremath{\rightarrow}}{r}\mathrm{metal}$转变。我们还发现，在液态CdTe中，在熔化温度附近，Te原子形成了无限支链。过冷阶段仍然存在短链和简化链。随着温度的升高，链断裂，变短，最终在过热状态下转变为紧密堆积的团簇。我们还研究了该体系的动力学和电学性质。
We perform ab initio molecular-dynamics simulations of CdTe at three different temperatures: 800 K (supercooled state), 1370 K (near the melting temperature), and 3000 K (superheated state). In agreement with experiment, we find that upon the melting, CdTe experiences a $\mathrm{semiconducto}\stackrel{\ensuremath{\rightarrow}}{r}\mathrm{semiconductor}$ transition. In its liquid state, CdTe retains its tetrahedral environment with the coordination number \ensuremath{\sim}4. We find that heating CdTe much above its melting point leads to substantial structural changes with a transformation to a more close-packed atomic structure. The coordination number of the superheated phase is \ensuremath{\sim}6 and the dc electrical conductivity is an order of magnitude larger than at the melting temperature. This, along with the disappearance of the finite band gap, suggests a gradual $\mathrm{semiconducto}\stackrel{\ensuremath{\rightarrow}}{r}\mathrm{metal}$ transition in the CdTe system at a temperature higher than melting point. We also find in liquid CdTe, near the melting temperature, atoms of Te form infinite branched chains. Short and simplified chains are still present in the supercooled phase. As the temperature increases, chains break, become shorter, and, eventually, transform to form close-packed clusters in the supeheated state. We also examine dynamical and electronic properties of the CdTe system.