氧化锌电子结构的压力效应的理论研究

基于平面波函数密度泛函理论研究了不同压力条件下纤锌矿结构氧化锌的晶格结构和电子结构。计算结果表明,氧化锌的晶格参数和Zn—O键长随外压力的增加先增大后逐渐减小,晶胞纵横轴长之比增大,晶格对称性保持不变;带隙类型均为直接带隙,其宽度随外压力增加先降低后逐渐增大,零压力下其存在着0.908eV的直接带隙,在最大压力100GPa下其带隙达0.993eV;费米能级附近的状态密度随压力增加有增大的趋势,电子局域化趋势明显。分析结果表明,随着外压力的增加,氧化锌费米能级下方附近的载流子有效质量先增大后减小;导带的载流子有效质量均较小。外界加力还改变了氧化锌体系的电子分布情况。     

Cu掺杂对ZnO氧化物电子结构与电输运性能的影响

采用平面波超软赝势密度泛函理论计算的方法研究了p型Cu掺杂的纤锌矿结构氧化物ZnO的电子结构,在此基础上分析了其电输运性能。计算结果表明,Cu掺杂ZnO氧化物具有0.6eV的直接带隙,且为p型半导体,在导带和价带中都出现了由Cu电子能级形成的能带,体系费米能级附近的能带主要由Cup态、Cud态和Op态电子构成,且他们之间存在着强相互作用。电输运性能分析结果表明,Cu掺杂的ZnO氧化物价带中的载流子有效质量较大,导带中的载流子有效质量较小;其载流子输运主要由Cup态、Cud态、Op态电子完成,且需要载流子（空穴和电子）跃迁的能隙宽度较未掺杂的ZnO氧化物减小。     

不同浓度Ti掺杂Ca2Si电子结构及光学性质的研究

采用第一性原理方法计算不同Ti含量Ca_2Si的几何结构、能带结构、电子态密度及光学性质。几何结构和电子结构的计算结果表明,Ti掺杂使Ca_2Si的晶格常数a增大,b、c减小,晶胞体积减小。Ca_(2-x)Ti_xSi的带隙变宽,其中掺杂浓度为4.2%时带隙最大为0.55 eV,费米面进入导带,导电类型为n型。Ti的掺入削弱了Ca的3d态电子贡献,费米能级附近电子态密度仍主要由Ca-3d态电子贡献。光学性质的计算结果表明,Ti掺入后介电函数虚部、吸收系数向低能端偏移,光学跃迁强度减弱,反射率在E=0 eV处增大。     

强电场对NiO电子结构性质的影响研究

基于平面波密度泛函理论研究了电场强度为10V?nm-1下立方结构氧化镍的电子结构性质。结果表明:立方相氧化镍在电场强度10V?nm-1下呈现导体的能带结构,价带上移到导带,态密度谱图在多个能量取得最值,局域化效应增强,费米能级附近的态密度增大为原系统的2倍多。费米能级上的载流子浓度由4 e/eV增大到15 e/eV,这源于Op、Nis、Nid态对费米面的贡献。强电场下的电子在不同量子状态之间显示了明显的转移,介电函数计算表明强电场下体系在0.32 eV附近具有最大的吸收,吸收峰峰值66.89。强电场明显调控了NiO的电学、光学和场致光吸收性能。     

Sb掺杂ZnO电子结构和光学性质

为了研究ZnO掺Sb后电子结构和光学性质的变化,采用基于密度泛函理论对纯净ZnO和Sb掺杂ZnO两种结构进行第一性原理的计算。计算结果表明：随着Sb的掺入,体系的晶格常数变大,键长增加,体积变大,系统总能增大。能带中价带和导带数目明显变密,费米能级进入导带,体系逐渐呈金属性,带隙明显展宽。在光学性质方面,主吸收峰的左边出现了新的吸收峰,是由导带上的Zn-4s和Sb-5p轨道杂化电子跃迁所致;同时介电函数虚部波峰发生一定程度的升高,实部静态介电常数也明显增大。     

应变层超晶格(ZnSe)_(2n)/(ZnS_xSe_(1-x))_(2n)的电子结构

本文用LCAO-Recursion方法研究了应变层超晶格(ZnSe)_(2n)/(ZnS_xSe_(1-x))_(2n)(n=1)的电子结构。计算了两种应变组态(赝晶生长,Free-Standing生长)下超晶格总的态密度,各原子的局域和分波态密度。我们发现:带隙E_g、费米能级E_f和原子价随应变的变化而变化;(ZnSe)_(2n)/(ZnS_xSe_(1-x))_(2n)超晶格中离子键和共价键共存;电子在界面附近发生了转移。     

Se和Cd掺杂GaN电子结构与光学性质的第一性原理研究

基于密度泛函理论的第一性原理,使用GGA+U方法分别计算Se和Cd单掺与共掺杂GaN体系的晶格常数、电子结构及光学性质.结果表明:与本征GaN相比,掺杂后体系的晶格常数发生了改变,禁带宽度减小,吸收光谱均发生红移,表明掺杂使体系的光谱响应范围得到更大拓展.其中,Cd单掺GaN体系的禁带宽度最小,并在费米能级附近有杂质能...     

基于第一性原理的Ga-Eu共掺ZnO光电性质的研究

采用基于密度泛函理论的第一性原理方法,分析了Ga-Eu共掺杂ZnO(GEZO)结构的能带结构、态密度、马利肯布居分布以及光学性质。结果表明,计算得到的晶格常数及带隙与实验值一致。Ga,Eu的掺入贡献了导电载流子,使体系的电导率增强。费米能级进入导带,呈现n型导电。从态密度中可知费米能级处出现了由Eu的4f态引入的杂质带,Ga也在导带底处贡献了4p和4s态。原子和键的平均马利肯布居分布表明,Ga,Eu原子的掺入增强了键的离子性。光学性质方面,Ga,Eu的掺入使得介电函数实部和虚部的峰位向低能区转移,吸收率和反射率在可见光区均有提高。     

空位缺陷金红石型TiO2电子结构和光学性质的理论研究

基于密度泛函理论(DFT)的第一性原理模守恒赝势 方法,对纯金红石型TiO₂和Ti、O两种空位缺 陷相的几何结构、能带结构、态密度(DOS)以及光学性质进行了 系统地对比研究。结果发现,含有空 位缺陷的TiO₂键长增大,原子布局值减小并出现微弱的磁性;空位缺陷导致导带变窄,导 带和价带 都向低能级方向移动,由空位原子贡献的载流子增强了体系的电导率,费米能级上移进入导 带;与 纯金红石型TiO₂的直接带隙宽度(3.0eV)相比较,Ti空位缺陷相转 变为P型半导体且直接带隙为1.816 eV,而O空位缺陷相转变为n型半导体且间接带隙为1.961eV。同时, 两种空位缺陷结构的介电峰显 著红移,折射率有明显变化,对可见光区的吸收系数均比纯TiO₂高。与O空位结构相比,Ti 空位结构的 介电常数、折射率、消光因子和对可见光的吸收强度更大,更能增强电子在低能端的光学跃 迁,具有更佳的可见光催化性能。     

一维声子晶体在防止低频噪声中的应用

应用集中质量法研究了集中质量数n、晶格常数a、组分比t、弹性模量E及密度ρ等因素对一维声子晶体带隙的影响.结果表明,带隙起始频率及带宽随a增加而减小,随t增加而快速增大(当t>1);带隙起始频率随两种材料E差值与ρ差值增加而减小,而带隙截止频率却不变;带隙精度则随n增加而增大.据此设计出一种能屏蔽约59～557 Hz范围内低频噪声的复合结构声子晶体.     

Sb掺杂SrTiO3电子结构的第一性原理计算

计算了Sb掺杂SrTi1-xSbxO3(x=0,0.125,0.25,0.33)体系电子结构,分析了掺杂对SrTiO3晶体的结构、能带、态密度、分波态密度的影响.所有计算都是基于密度泛函理论框架下的第一性原理平面波超软赝势方法.计算结果表明:体系的导电性与掺杂浓度有关,Sb掺杂在母体化合物SrTiO3中引入了大量的传导电子,费米能级进入导带.当Sb掺杂浓度x=0.125时,体系显示金属型导电性.同时,光学带隙展宽,且向低能方向漂移,可作为优良的透明导电薄膜材料.     

Sb掺杂SrTiO3电子结构的第一性原理计算

计算了Sb掺杂SrTi1-xSbxO3(x=0,0.125,0.25,0.33)体系电子结构,分析了掺杂对SrTiO3晶体的结构、能带、态密度、分波态密度的影响.所有计算都是基于密度泛函理论框架下的第一性原理平面波超软赝势方法.计算结果表明:体系的导电性与掺杂浓度有关,Sb掺杂在母体化合物SrTiO3中引入了大量的传导电子,费米能级进入导带.当Sb掺杂浓度x=0.125时,体系显示金属型导电性.同时,光学带隙展宽,且向低能方向漂移,可作为优良的透明导电薄膜材料.     

First-Principles Study of the Electronic Structure and Thermoelectric Properties of Al-Doped ZnO

ZnO materials doped with elements such as Al, Ga, etc. are of great interest for high-temperature thermoelectric applications. In this work, the effects of Al doping on the electronic structure and thermoelectric properties of the ZnO system are presented. The energy band structure and density of states of Al-doped ZnO were investigated using the projector-augmented plane wave pseudopotential method within the local density approximation. The calculated energy band structure was then used in combination with the Boltzmann transport equation to calculate the thermoelectric parameters of Al-doped ZnO. The electronic structure calculation showed that the position of the Fermi level of the doped sample was shifted to a higher energy level compared with the undoped material. The conduction band near the Fermi energy was a combination of hybridized Zn sp-orbitals and Al s-orbital. The calculated thermoelectric properties were compared with the experimental results, showing some agreement. For the Al-doped ZnO system, the Seebeck coefficient was shown to be negative and its absolute value increased with temperature. The electrical conductivity and electronic thermal conductivity followed the trend of the experimental results.     

碱金属掺杂SnO2材料的电子结构和光学性质

文章基于第一性原理研究了碱金属掺杂的SnO2的能带结构以及态密度.研究结果表明:掺杂能够使能级增多,很好地调节带隙值.Li,Na,K,Rb掺杂的SnO2材料,价带顶有能级穿过费米线,材料呈现出半导体特性.其中Rb掺杂使材料在费米面附近产生杂质能级.而Cs,Fr掺杂的SnO2材料,价带顶向低能级方向移动,费米能级不再穿过价带,费米线附近出现轨道杂化,两者相比Fr掺杂使费米面附近能级分布更加离散.掺杂后SnO2的反射率变化主要体现在可见光以及紫外区域,吸收边发生了红移,对实现SnO2光催化起很大作用.     

氧化锌p型共掺杂精细结构的第一性原理研究

计算了ZnO材料p型掺杂精细结构,分析了p型掺杂ZnO晶体的电子结构、电荷布局、电子态密度、差分电荷。所有计算都是基于密度泛函理论(DFT)框架下的第一原理平面波超软赝势方法。计算结果表明:掺杂Ⅴ族元素(N、P、As、In)的氧化锌材料在能隙中引入了深受主能级,载流子(空穴)局域于价带顶附近。而利用加入激活施主的共掺杂技术的计算结果却表明,受主能级向低能方向移动,形成了浅受主能级。同时,受主能级带变宽,非局域化特征明显。     

Thermoelectric properties of Al-doped ZnO: experiment and simulation

Advancement in doping other elements, such as Ce, Dy, Ni, Sb, In and Ga in ZnO^[1], have stimulated great interest for high-temperature thermoelectric application. In this work, the effects of Al-doping in a ZnO system on the electronic structure and thermoelectric properties are presented, by experiment and calculation.Nanosized powders of Zn_1-xAl_xO (x=0, 0.01, 0.02, 0.03 and 0.06) were synthesized by hydrothermal method. From XRD results, all samples contain ZnO as the main phase and ZnAl₂O₄ (spinel phase) peaks were visible when Al additive concentrations were just 6 at%. The shape of the samples changed and the particle size decreased with increasing Al concentration. Seebeck coefficients, on the other hand, did not vary significantly. They were negative and the absolute values increased with temperature. However, the electrical resistivity decreased significantly for higher Al content.The electronic structure calculations were carried out using the open-source software package ABINIT^[2], which is based on DFT. The energy band gap, density of states of Al-doped ZnO were investigated using PAW pseudopotential method within the LDA+U. The calculated density of states was then used in combination with the Boltzmann transport equation^[3] to calculate the thermoelectric parameters of Al-doped ZnO. The electronic band structures showed that the position of the Fermi level of the doped sample was shifted upwards in comparison to the undoped one. After doping Al in ZnO, the energy band gap was decreased, Seebeck coefficient and electrical conductivity were increased.Finally, the calculated results were compared with the experimental results. The good agreement of thermoelectric properties between the calculation and the experimental results were obtained.     

Tuning the Electronic Properties of Graphene Oxide Nanoribbons Through Different Oxygen Doping Configurations

The electronic properties of armchair graphene oxide nanoribbons (AGONRs) with different doped oxygen configurations are studied based on density functional theory using first principle calculations. The electronic properties of the AGONRs are tuned by different oxygen configurations for top edges, center, bottom edges and fifth width. The AGONRs for top-edge O doping configuration are indirect band gap semiconductors with an energy gap of 1.268 eV involving hybridization among C-2p and O-2s, 2p electrons and electrical conductivity of oxygen atoms. The center and bottom edges are direct band gap semiconductors with 1.317 eV and 1.151 eV, respectively. The valence band is contributed from C-2p, O-2p and H-1s for top-edge O doping. The electronic properties of AGONRs are changed due to localization in ?2.94 eV of O-2p states. The center O-doped AGONRs are n-type semiconductors with Fermi levels near the conduction band bottom. This is due to hybridization among C-2s, 2p and O-2p electrons. However, bottom-edge O-doped AGONRs are p-type semiconductors, due to the electrical conductivity of oxygen atoms. The fifth-width O-doped AGONRs are indirect band gap semiconductors with an energy gap of 0.375 eV. The projected density of states shows that the localization and hybridization between C-2 s, 2p, O-2p and H-1s electronic states are rising in the conduction band and valence band from the projected density of states. The localization is induced by O-2p electronic states at a Fermi level.