Mn2+、N2-共掺杂Zn2GeO4晶体电子结构和光学性质的研究

采用基于密度泛函理论的平面波超软赝势方法对本征Zn2GeO4，Mn2+掺杂Zn2GeO4，Mn2+/N2-共掺杂Zn2GeO4超晶胞进行了几何结构优化，计算了掺杂前后体系的晶格常数、能带结构、态密度和光学性质。结果表明，Mn离子掺入后，Mn离子3d轨道与O离子2p轨道之间有强烈的轨道杂化效应，掺杂系统不稳定，而Mn/N离子共掺后，Mn离子和N离子之间的吸引作用克服了Mn离子之间的排斥作用，能够明显地提高掺杂浓度和体系的稳定性。光学性质计算结果表明，Mn离子与N离子共掺杂能改善Zn2GeO4电子在低能区的光学跃迁特性，增强电子在可见光区的光学跃迁；吸收谱计算结果显示，Mn离子与N离子掺入后体系对低频电磁波吸收增加。     

Interface effect between blue phosphorus and metals

The contacted properties of metal substrates with single layer (monolayer) blue phosphorus are calculated by first principles. We analyze the charge transfer, atomic orbital overlap, electronic properties and potential barrier at the interface of metal contacted blue phosphorene (BuleP) to understand how to effectively inject electrons from the metal into the contacted blue phosphorus. We inquire into interfacial effect of blue phosphorene directly in contact with five representative metallic substrates – Au (111), Ag(111), Al(111), Co(111) and Sc(0001), which are having minimal lattice mismatch with the BlueP. We find that the contact properties of these five metals are ohmic contact and schottky contact. Of the five different contact metals, Co-BlueP heterojunction has the best electrical conductivity. The lower SBH in the Al contact can also lead to a good substrate for a Schottky contact for the heterojunction. These results can provide guidance for the future design of BlueP-based electronic devices and for the exploration of new low-dimensional semiconductor transport processes.     

A Theoretical study on the charge and discharge states of Na-ion battery cathode material,Na1+xFePO4F

Na₂FePO₄F is a promising cathode material for a Na-ion battery because of its high electronic capacity and good cycle performance. In this work, first principle calculations combined with cluster expansion and the Monte Carlo method have been applied to analyze the charge and discharge processes of Na₂FePO₄F by examining the voltage curve and the phase diagram. As a result of the density functional theory calculation and experimental verification with structural analysis, we found that the most stable structure of Na_1.5FePO₄F has the P2₁/b11 space group, which has not been reported to date. The estimated voltage curve has two clear plateaus caused by the two-phase structure composed of P2₁/b11 Na_1.5FePO₄F and Pbcn Na₂FePO₄F or Na₁FePO₄F and separated along the c-axis direction. The phase diagram shows the stability of the phase-separated structure. Considering that Na₂FePO₄F has diffusion paths in the a- and c-axis directions, Na₂FePO₄F has both innerphase and interphase diffusion paths. We suggest that the stable two-phase structure and the diffusion paths to both the innerphase and interphases are a key for the very clear plateau. We challenge to simulate a nonequilibrium state at high rate discharge with high temperature by introducing a coordinate-dependent chemical potential. The simulation shows agreement with the experimental discharge curve on the disappearance of the two plateaus. © 2018 Wiley Periodicals, Inc.     

Effect of Zr concentration on the mechanical and thermodynamic properties of NbIr3 intermetallic compounds from theoretical estimations

ABSTRACT

The iridium is an important metal which has excellent resistance to corrosion at high temperature. L1₂ intermetallic compounds i.e. Ir₃Nb and Ir₃Zr, with similar lattice parameters are ideal for working at high temperature. They are fully soluble due to their low lattice misfit. A first-principle investigation into the effect of doping Zr with different concentrations on the electronic structure, mechanical and thermodynamic properties of NbIr₃ has been studied to prompt the development of novel high-temperature materials. Nine Zr_xNb_8?xIr₂₄ compounds are carefully considered. The results show that adding Zr into these compounds can strengthen their structural stability and ductility. Nevertheless, it reduces the elastic modulus and elastic stiffness. Simultaneously, with the increase of Zr content, the thermodynamic properties of these compounds decrease. It is also found that the changes of elastic modulus are mainly attributed to the variations of bonds in these compounds.     

基于Aspen Plus耦合生命周期评价的科研案例在环境工程原理教学中的应用

将化工流程模拟Aspen Plus软件与环境影响评估领域常用的生命周期评价(LCA)进行集成应用,围绕环境工程原理教学中有关化工过程质量能量衡算与环境污染防治内容的协同应用与拓展,构建化工流程模拟-环境风险评估科研案例“苯酐生产流程模拟及环境风险研究”,并将其作为环境工程原理的综合教学案例。教学实践经验表明,通过引入工程相关综合教学案例,不仅使得抽象的理论知识更加生动具体,而且在深化学生对课程理论知识理解的同时,提高学生应用专业知识分析和解决化工生产环境污染工程问题的综合能力和素质,为学生将来步入相关领域工作奠定扎实的基础。     

Cu-Doped MoSi2N4 Monolayer as a Potential NH3 Sensor

Cu doped MoSi₂N₄ monolayer (Cu-MoSi₂N₄) was firstly proposed to analyze adsorption performances of common gas molecules including O₂, N₂, CO, NO, NO₂, CO₂, SO₂, H₂O, NH₃ and CH₄ via density functional theory (DFT) combining with non-equilibrium Green's function (NEGF). The electronic transport calculations indicate that Cu-MoSi₂N₄ monolayer has high sensitivity for CO, NO, NO₂ and NH₃ molecules. However, only NH₃ molecule adsorbs on the Cu-MoSi₂N₄ monolayer with moderate strength (−0.55 eV) and desorbs at room temperature (2.36×10⁻³ s). Thus, Cu-MoSi₂N₄ monolayer is demonstrated as a potential NH₃ sensor.     

Deformation of single‐walled carbon nanotubes by interaction with graphene: A first‐principles study

The interaction between single‐walled carbon nanotubes (SWNTs) and graphene were studied with first‐principles calculations. Both SWNTs and single‐layer graphene (SLG) or double‐layer graphene (DLG) display more remarkable deformations with the increase of SWNT diameter, which implies a stronger interaction between SWNTs and graphene. Besides, in DLG, deformation of the upper‐layer graphene is less than in SLG. Zigzag SWNTs show stronger interactions with SLG than armchair SWNTs, whereas the order is reversed for DLG, which can be interpreted by the mechanical properties of SWNTs and graphene. Density of states and band structures were also studied, and it was found that the interaction between a SWNT and graphene is not strong enough to bring about obvious influence on the electronic structures of SWNTs. © 2015 Wiley Periodicals, Inc.     

材料弹塑性性能数值模拟的多尺度方法

将均匀化方法和渐近分析(Asymptotic Analysis)与参变量变分原理相结合提出了一种模拟复合材料非线性性能的多尺度数值方法.该方法用渐近分析建立宏-细观变量之间的联系,利用参变量变分原理计算非线性响应,求解过程采用迭代算法.为提高计算精度,针对Von-Mises准则和Tsai-Hill准则,提出了一个基于参变量变分原理的改进算法,算例表明该方法可以显著消除传统方法采用线性展开式构造线性互补条件所带来的误差.