物理化学学报2018，Vol.34Issue(10)：1116-1123,8.DOI:10.3866/PKU.WHXB201801151
采用优化的DFTB参数对铜(111)表面碳二聚化的分子动力学研究
A Molecular Dynamics Study of Carbon Dimerization on Cu(111) Surface with Optimized DFTB Parameters
摘要
Abstract
Cu has been widely used as a substrate material for graphene growth.To understand the atomistic mechanism of growth,an efficient and accurate method for describing Cu-C interactions is necessary,which is the prerequisite of any possible large-scale molecular simulation studies.The semi-empirical density-functional tight-binding (DFTB) method has a solid basis from the density functional theory (DFT) and is believed to be a good tool for achieving a balance between efficiency and accuracy.However,existing DFTB parameters cannot provide a reasonable description of the Cu surface structure.At the same time,DFTB parameters for Cu-C interactions are not available.Therefore,it is highly desirable to develop a set of DFTB parameters that can describe the Cu-C system,especially for surface reactions.In this study,a parametrization for Cu-C systems within the self-consistent-charge DFTB (SCC-DFTB) framework is performed.One-center parameters,including on-site energy,Hubbard,and spin parameters,are obtained from DFT calculations on free atoms.Two-center parameters can be calculated based on atomic wavefunctions.The remaining repulsive potential is obtained as the best compromise to describe different kinds of systems.Test calculations on Cu surfaces and Cu-or C atom-adsorbed Cu surfaces indicate that the obtained parameters can generate reasonable geometric structures and energetics.Based on this parameter set,carbon dimerization on the Cu(111) surface has been investigated via molecular dynamics simulations.Since they are the feeding species for graphene growth,it is important to understand how carbon dimers are formed on the Cu surface.It is difficult to observe carbon dimerization in brute-force MD simulations even at high temperatures,because of the surface structure distortion.To study the dimerization mechanism,metadynamics simulations are performed.Our simulations suggest that carbon atoms will rotate around the bridging Cu atom after a bridging metal structure is formed,which eventually leads to the dimer formation.The free energy barrier for dimerization at 1300 K is about 0.9 eV.The results presented here provide useful insights for understanding graphene growth.关键词
铜表面/碳二聚体/DFTB/分子模拟Key words
Copper surface/Carbon dimer/DFTB/Molecular simulation分类
化学化工引用本文复制引用
殷迪,邱宗仰,李湃,李震宇..采用优化的DFTB参数对铜(111)表面碳二聚化的分子动力学研究[J].物理化学学报,2018,34(10):1116-1123,8.基金项目
The project was supported by National Natural Science Foundation of China (21573201),the Ministry of Science and Technology of China (2016YFA0200604),and the Special Program for Applied Research on Super Computation of the National Nature Science Foundation of China-Guangdong Joint Fund (U1501501).国家自然科学基金(21573201),科学技术部(2016YFA0200604)及国家自然科学基金-广东联合基金(第二期)超级计算科学应用研究专项(U1501501)资助 （21573201）
