F原子吸附TiO_2:Mn(001)稀磁半导体薄膜电子结构和磁性的第一性原理计算

利用第一性原理方法计算Mn离子掺杂纯净TiO2(001)和F原子吸附的TiO2(001)薄膜的形成能、态密度和磁矩.F原子吸附明显降低TiO2∶Mn薄膜体系的形成能.F原子的吸附导致Mn离子的磁矩减小,而表面O原子的磁矩增大.表面O原子的磁矩主要来源于O原子p x和p y轨道的自旋极化,研究表明表面吸附F原子更有利于Mn离子的掺杂,在一定程度上有利于获得结构稳定的铁磁态半金属特性的TiO2∶Mn薄膜.     

Synthesis of boron,nitrogen co-doped porous carbon from asphaltene for high-performance supercapacitors

Oxidized asphaltene(OA), a thermosetting material with plenty of functional groups, is synthesized from asphaltene(A) using HNO3/H2SO4as the oxidizing agent. Boron, nitrogen co-doped porous carbon(BNC–OA) is prepared by carbonization of the mixture of boric acid and OA at 1173 K in an argon atmosphere. X-ray photoelectron spectroscopy(XPS) characterization reveals that the BNC–OA has a nitrogen content of 3.26 at.% and a boron content of 1.31 at.%, while its oxidation-free counterpart(BNC–SA) has a nitrogen content of 1.61 at.% and a boron content of 3.02 at.%. The specific surface area and total pore volume of BNC–OA are 1103 m2·g-1and 0.921 cm3·g-1, respectively. At a current density of0.1 A·g-1, the specific capacitance of BNC–OA is 335 F·g-1and the capacitance retention can still reach 83% at 1 A·g-1.The analysis shows that the superior electrochemical performance of the BNC–OA is attributed to the pseudocapacitance behavior of surface heteroatom functional groups and an abundant pore-structure. Boron, nitrogen co-doped porous carbon is a promising electrode material for supercapacitors.     

聚偏氟乙烯β相全反式结构链的第一性原理计算

用紧束缚的Hartree-Fock自洽场方法对聚偏氟乙烯(PVDF)β相的全反式结构链进行了第一性原理计算.在结构方面,计算得出,相邻F原子对平均距离为0264nm 相邻H原子对平均距离为0255nm 和F原子相连的C原子的平均距离为0.260nm 和H原子相连的C原子的平均距离为0.257nm.电偶极矩方面,计算得出单体的平均电偶极矩为3.98×10-30C·m(三个单体的链) 4.40×10-30C·m(六个单体的链) 4.44×10-30C·m(十一个单体的链).结构和电偶极矩的计算值与实验值基本符合.最后预测了全反式链的振动模式 关键词： 聚偏氟乙烯β相全反式结构链 Hartree-Fock自洽场方法     

First principles study on the ferroelectricity of the perovskite ABO3 ferroelectrics

In order to understand well the different ferroelectric behaviour of quantum paraelectrics and ferroelectrics and the origin of the ferroelectricity of the solid solution KTa0.5Nb0.5O3(KTN),we calculated the electronic structure of CaTiO3,BaTiO3 and KTN by first principles calculation.From total energy analysis,it is shown that,with increasing cell volume,the crystals (CaTiO3,SrTiO3) will have a ferroelectric instability.For BaTiO3,the ferroelectricity will disappear as the cell volume is decreased.From the density of states analysis,it is shown that the hybridization between B d and O p is very important for the ferroelectric stability of ABO3 perovskite ferroelectrics.This is consistent with the analysis of band structure.     

三维无机-有机杂化骨架微孔材料Zn3(bpdc)3(4,4'-bpy)·DMF·2H2O的合成与结构

合成了一个具有三维骨架结构的无机-有机杂化微孔材料Zn3(bpdc)3(4,4'-bpy)@DMF@2H2O,并通过ICP和X射线单晶衍射分析等手段对其结构进行了表征.晶体属于正交晶系,Pbcn空间群,晶胞参数a=1.4532(3)nm,b=2.50327(5)nm,c=1.8184(4)nm,V=6.616(2)nm3,Z=8,Dc=1.296g/cm3,Mr=645.58,μ=1.145mm-1,F(000)=2656.最后的一致性因子为R=0.0705,Rw=0.2056.     

基于改进遗传PID算法的能量回馈制动系统

针对目前能量回馈系统效率低的问题, 提出一种基于改进的遗传PID（比例-积分-微分）算法对能量回馈系统进行控制. 首先建立回馈制动的数学模型, 然后根据其模型采用仿真软件（MATLAB）, 并结合改进的遗传PID算法进行仿真实验. 实验结果表明, 改进的遗传PID算法比传统PID算法控制效果更好, 稳定性、 鲁棒性及抗干扰能力更强, 且回收效率提高了25.8%.     

Peptide friction in water nanofilm on mica surface

Peptide frictions in water nanofilms of various thicknesses on a mica surface are studied via molecular dynamics simulations. We find that the forced lateral motion of the peptide exhibits stick-slip behaviour at low water coverage; in contrast, the smooth gliding motion is observed at higher water coverage. The adsorbed peptide can form direct peptide-surface hydrogen bonds as well as indirect peptide-water-surface hydrogen bonds with the substrate. We propose that the stick-slip phenomenon is attributed to the overall effects of direct and indirect hydrogen bonds formed between the surface and the peptide.     

Stability and electronic structure studies of LaAlO_3/SrTiO_3 (110) heterostructures

The first-principles calculations are employed to investigate the stability, magnetic, and electrical properties of the oxide heterostructure of LaAlO3/SrTiO3(110). By comparing their interface energies, it is obtained that the buckled interface is more stable than the abrupt interface. This result is consistent with experimental observation. At the interface of LaAlO3/SrTiO3(110) heterostructure, the Ti–O octahedron distortions cause the Ti t2 gorbitals to split into the twofold degenerate dxz/dyz and nondegenerate dxy orbitals. The former has higher energy than the latter. The partly filled two-fold degenerate t2 gorbitals are the origin of two-dimensional electron gas, which is confined at the interface. Lattice mismatch between LaAlO3 and SrTiO3leads to ferroelectric-like lattice distortions at the interface, and this is the origin of spin-splitting of Ti 3d electrons. Hence the magnetism appears at the interface of LaAlO3/SrTiO3(110).     

软凝聚态物质的研究现状及其发展前景

介绍软凝聚态物质不同领域的共同基本特点和一般规律,以及软凝聚态物质研究工作在国内外的发展现状和近期有可能取得的突破性进展.