Atta-Fynn Raymond, Biswas Parthapratim
Department of Physics and Astronomy, The University of Texas, Arlington, TX 76019, USA.
J Phys Condens Matter. 2009 Jul 1;21(26):265801. doi: 10.1088/0953-8984/21/26/265801. Epub 2009 Jun 3.
Localized basis ab initio molecular dynamics simulation within the density functional framework has been used to generate realistic configurations of amorphous silicon carbide (a-SiC). Our approach consists of constructing a set of smart initial configurations that conform to essential geometrical and structural aspects of the materials obtained from experimental data, which is subsequently driven via a first-principles force field to obtain the best solution in a reduced solution space. A combination of a priori information (primarily structural and topological) along with the ab initio optimization of the total energy makes it possible to model a large system size (1000 atoms) without compromising the quantum mechanical accuracy of the force field to describe the complex bonding chemistry of Si and C. The structural, electronic and vibrational properties of the models have been studied and compared to existing theoretical models and available data from experiments. We demonstrate that the approach is capable of producing large, realistic configurations of a-SiC from first-principles simulation that display its excellent structural and electronic properties. Our study reveals the presence of predominant short range order in the material originating from heteronuclear Si-C bonds with a coordination defect concentration as small as 5% and a chemical disorder parameter of about 8%.
在密度泛函框架内进行的局域基从头算分子动力学模拟已被用于生成非晶硅碳化物（a-SiC）的真实构型。我们的方法包括构建一组符合从实验数据获得的材料基本几何和结构特征的智能初始构型，随后通过第一性原理力场驱动，在缩小的解空间中获得最佳解。先验信息（主要是结构和拓扑信息）与总能量的从头算优化相结合，使得在不影响力场量子力学精度以描述Si和C复杂键合化学的情况下，能够对大尺寸系统（1000个原子）进行建模。对模型的结构、电子和振动性质进行了研究，并与现有的理论模型和实验数据进行了比较。我们证明，该方法能够通过第一性原理模拟生成大尺寸、真实的a-SiC构型，展现出其优异的结构和电子性质。我们的研究揭示了材料中存在主要的短程有序，其源于异核Si-C键，配位缺陷浓度低至5%，化学无序参数约为8%。
