三氧化钨电致变色薄膜最佳掺杂含量的理论计算

介绍电致变色薄材料最佳掺杂含量的定量理论。该理论建立了电子薄膜材料的某一物理性能与晶体结构、制备方法和掺杂剂含量之间的联系，给出了一个能够拟合实验曲线的具有确定物理意义的抛物线方程。该方程的极值点确定了最佳掺杂含量与晶体结构和制备方法之间的定量关系，进而得到了一个最佳掺杂含量的表达式。分析三氧化钨电致变色薄膜材料的掺杂改性的实验结果，应用最佳掺杂含量表达式定量计算了三氧化钨以及三氧化钼电致变色薄膜材料的最佳掺杂含量，定量计算的结果与实验数据相符合。该理论方法也适用于其他材料最佳掺杂粒子数分数的理论计算。     

B,N协同掺杂金刚石电子结构和光学性质的第一性原理研究

基于金刚石的稳定结构, 在实验研究的基础上, 本文采用基于周期性密度泛函理论计算了B/N单掺杂、共掺杂金刚石的晶体结构, 并就掺杂方式和掺杂后形成能进行了对比研究, 得到了B/N双掺杂的最稳定结构. 在此基础上, 进一步计算了N单掺杂及B/N共掺杂最稳定结构的吸收光谱、电子结构和态密度. 通过与实验结果对比可以看出, 较N单掺杂, B/N共掺杂的吸收光谱发生明显红移, 与实验符合较好. 计算结果表明: N原子单掺杂优先于B原子; 由于原子间的协同作用, B/N近邻共掺杂体系的形成能最低, 为掺杂的最可能结构.     

氮化铟p型掺杂的第一性原理研究

采用基于密度泛函理论(DFT)的总体能量平面波超软赝势法，对Mg，Zn，Cd掺杂InN的32原子超原胞体系进行了几何结构优化，从理论上给出了掺杂和非掺杂体系的晶体结构参数，其中非掺杂体系的理论值与实验值符合很好. 计算了掺杂InN晶体的结合能，总体态密度、集居数，差分电荷密度，并对此做了细致的分析. 计算结果表明，相对于Zn和Cd，Mg_In在InN中的溶解度会更大，并能提供更多的空穴态，非常有利于InN的p型掺杂. 关键词： 氮化铟 p型掺杂 电子结构 第一性原理     

锐钛矿TiO2及其掺Fe所导致的红移现象研究：赝势计算和紫外光谱实验

采用平面波超软赝势方法研究了锐钛矿型TiO2及Fe掺杂TiO2的晶体结构和能带结构，计算表明Fe掺杂导致TiO2电子局域能级的出现及禁带变窄，从而导致吸收光谱红移.研究发现，t2g态在红移现象中起了重要作用.紫外透射光谱实验证实了TiO2掺Fe后吸收光谱红移和禁带变窄的理论预言. 关键词： 密度泛函理论 TiO2 Fe掺杂 红移     

K-2N双受主共掺杂P型ZnO的第一性原理研究

本文采用基于第一性原理的密度泛函理论(DFT)平面波超软赝势方法,计算了未掺杂ZnO和K,K-2N掺杂ZnO体系的晶体结构、能带、电子态密度与光学性质.研究表明:K掺杂ZnO体系,带隙变宽,在费米能级附近引入了较浅的受主能级,费米能级进入到价带中.而K-2N共掺杂体系中,带隙变窄,形成了浅受主能级,这个对改善ZnO的p...     

Zn，O共掺杂实现p型AIN的第一性原理研究

基于密度泛函理论（density functional theory），采用第一性原理平面波超软赝势法，研究了纤锌矿AIN，Zn掺杂和Zn，O共掺杂AIN的晶体结构、能带、电子态密度、差分电荷分布及电荷布居数,计算结果表明：Zn，O共掺杂方法中引入激活施主O原子，能使受主能级向低能方向移动，形成了浅受主能级,同时，受主能带变宽、非局域化特征明显、从而提高了Zn原子的掺杂浓度和系统的稳定性,Zn，O共掺杂更有利于获得P型AIN．     

Pt-N共掺杂锐钛矿TiO_2的第一性原理研究

采用基于密度泛函理论(DFT)的第一性原理中的平面波超软赝势(PWPP)方法对理想TiO_2,N单掺杂,Pt单掺杂和Pt-N共掺杂锐钛矿相TiO_2的电子结构进行计算,分析N单掺杂、Pt单掺杂及Pt-N共掺杂对锐钛矿相TiO_2的晶体结构、能带和态密度的影响.计算结果表明:掺杂后TiO_2的晶格发生畸变,原子间键长的变化使晶格发生膨胀,Pt单掺杂、N单掺杂TiO_2禁带宽度变窄,Pt-N共掺杂TiO_2分别在价带顶和导带底产生杂质能级,且禁带宽度缩小范围大,表明Pt-N共掺杂能进一步提高锐钛矿TiO_2催化性能.     

K-2N双受主共掺杂P型ZnO的第一性原理研究

本文采用基于第一性原理的密度泛函理论（DFT）平面波超软赝势方法,计算了未掺杂ZnO和K,K-2N掺杂ZnO体系的晶体结构、能带、电子态密度与光学性质。研究表明：K掺杂ZnO体系,带隙变宽,在费米能级附近引入了较浅的受主能级,费米能级进入到价带中。而K-2N共掺杂体系中,带隙变窄,形成了浅受主能级,这个对改善ZnO的p型掺杂有重要意义。另一方面,掺杂后ZnO的光学性质也发生了一定变化,ZnO吸收谱中出现了新的吸收峰,同时介电函数虚部都出现了新的波峰,静态介电常数 也都增大了。     

Zn,Cd掺杂AlN电子结构的第一性原理计算

基于密度泛函理论(DFT)框架下的第一性原理的平面波超软赝势方法(USPP),对Zn,Cd掺杂AlN的32原子超原胞体系进行了几何结构优化,从理论上给出了掺杂和非掺杂体系的晶体结构参数。计算了掺杂AlN晶体的结合能、电子态密度、差分电荷密度,并对计算结果进行了细致的分析。计算结果表明,Cd、Zn都可以提供很多的空穴态,是良好的p型掺杂剂,但是相对于Cd, Zn原子在AlN晶体中的溶解度更大,并且可以提供更多的空穴,有利于形成更好的p型电导。     

3C-SiC材料p型掺杂的第一性原理研究

采用基于第一性原理的密度泛函理论平面波超软赝势法,研究了SiC材料p型掺杂的晶体结构和电子结构性质,得到了优化后体系的结构参数,掺杂形成能,能带结构和电子态密度,计算得到掺杂B,Al,Ga在不同浓度下的禁带宽度.结果表明:随着掺杂B原子浓度的增大,禁带宽度随之减小;而随着掺杂Al,Ga原子浓度的增大,禁带宽度随之增大;在相同浓度下,掺杂Ga的禁带宽度大于掺杂Al,掺Al禁带宽度大于掺B. 关键词： SiC 电子结构 掺杂 第一性原理软件     

ZnO:Mn as a member of II-VI:Mn family

ZnO:Mn thin films are grown by the metal organic chemical vapor deposition technique. Mn (x) varies in the 0<x<0.44 range. Vegard’s law has been verified for the lattice parameters. Electron paramagnetic resonance (EPR) measurements prove the substitutional incorporation of Mn²⁺ on zinc sites. The behavior of the EPR line width regarding temperature is discussed. All ZnO:Mn layers show antiferromagnetic interaction and a J₁/k_B=-15 K effective exchange constant. The optical band gap of ZnO:Mn increases with the manganese concentration. Raman spectroscopy reveals a Mn-related scattering band. PACS 71.55.Gs; 75.50.Pp; 61.10.Nz; 76.30.Fc; 75.30.Et; 78.40.-q     

Energy Structure of an Individual Mn Acceptor in GaAs : Mn

The energy structure of the Mn acceptor, which is a complex of Mn²⁺ ion plus valence band hole, is investigated in the external magnetic field and under presence of an uniaxial stress has been studied. The spin-flip Raman spectra are studied under resonant excitation of exciton bound to the Mn acceptor. The gfactors of the ground F = 1 and the first excited F = 2 states are determined and selection rules for the optical transitions between the acceptor states are described. The value of the random field (stress or electric field) acting on manganese acceptor and the deformation potential for the exchange interaction constant of the Mn²⁺ + hole complex are obtained. A theoretical model is developed that takes into account the influence of random internal and uniaxial external stress and magnetic field. The proposed model describes well the lines of spin-flip Raman scattering of Mn acceptor.     

Distance distributions about Mn in icosahedral and crystalline Al Mn Si

We report EXAFS measurements on icosahedral and orthorhombic Al₆Mn, icosahedral Al₇₄Mn₂₀Si₆, and α-Al₁₀₀Mn₂₄Si₁₄. We find close resemblance between α-phase and i-Al₇₄Mn₂₀Si₆, and poorer agreement between α-phase and i-Al₆Mn. Neither icosahedral phase showed much resemblance to the orthorhombic phase. We conclude that the icosahedral Al₇₄Mn₂₀Si₆ resembles a distorted α-phase, and so may be built of icosahedral glued together with Al as in the α structure. Icosahedral Al₆Mn is perhaps a more disordered version of the above.     

Gamma-ray spectroscopy of 25 57 Mn32 and 25 58 Mn33

The decays of ₂₅⁵⁷Mn₃₂ and ₂₅⁵⁸Mn₃₃ have been studied with the 8π Spectrometer following the reaction ⁴⁸Ca(¹³C,pxn)^{60 − x} Mn at a beam energy of 40 MeV. The level schemes of these two nuclei have been extended, and the multipolarities of the observed transitions have been determined.     

Pressure dependence of the magnetisation and Mn nmr of Mn4N

Abstract

The expanded lattice material Mn₄N contains two types of Mn site. The ⁵⁵Mn NMR at the Mn(I) site has been measured to 9 kbar at 77K. The Mn(I) NMR frequency, and the magnetisation, increased with pressure which is attributed to a decrease in the magnitude of the moment at the Mn(II) site.     

Hyperfine interaction in Ni79Mn21 and Ni76Mn24

We report on PAC measurements revealing very different magnetic behaviour in two nearby alloys. The Ni₇₉Mn₂₁ alloy orders at T_C=280(5) K, but a two field sites interpretation is needed. Both hyperfine fields (hff) are in the ratio 12 and their distributions have the same absolute width, the relative abundance of the high field site is 30%. A slope change in the hff (T) curve at low temperature may indicate the transition into the mixed state. In the Ni₇₆Mn₂₄ alloy we observe magnetic ordering at T=95(3) K followed by a smooth increase of the effective hff upon cooling but with an anomalous minimum around T=20 K.