Sb掺杂LiBiO3电子结构的第一性原理计算

通过能带结构、电子态密度、电子局域化函数、Bader电荷等方面的密度泛函理论(DFT)第一性原理计算,对掺杂了Sb的LiBiO3的电子结构进行研究,试图从理论角度探寻合适的光催化材料。计算结果表明,空间群为Pccn的正交LiBiO3为直接半导体,DFT计算带隙为0.23eV,而采用HSE泛函形式的计算带隙为1.18eV,较为接近实验测定值。随着Sb掺杂量的增加,LiBi1-xSbxO3的计算带隙逐渐加大,与纯LiBiO3相比,Sb掺杂体系中出现了具有更强键合作用的Sb-O键,有利于改善体系的光催化性能。     

实现照明 LED 用 p-ZnO 中 Ag-2N高共掺粒子数分数机理

基于密度泛函理论的第一性原理方法,对六方纤锌矿结构的Zn O晶体,N、Ag分别掺杂Zn O,以及Ag-2N共掺杂Zn O晶体的几何结构分别进行了比较研究,在此基础上计算得到了未掺杂Zn O晶体和不同掺杂情况下Zn O晶体的能带结构、总体态密度、分波态密度和电荷布居数.结果显示:Ag-2N共掺杂Zn O具有较稳定的结构,能有效提高载流子粒子数分数,更容易得到稳定的p型Zn O.     

聚噻吩导电性能理论分析

利用Gaussian 03从头算程序,采用密度泛函理论(DFT)对导电高分子材料噻吩寡聚体进行了结构与性能关系讨论.选择B3LYP泛函,在B3LYP/6-31 G(d)基组水平下对没有电荷掺杂(nT,n=1/2,1,3/2,2,5/2,3)和有电荷掺杂(nT ,n=1/2,1,3/2,2,5/2,3)的1-6个环的噻吩寡聚体进行了几何全优化计算,对得到的几何结构、前线轨道能级差和激发能等进行分析发现,聚噻吩导电性能随着链长的增加而增加.链长增加到一定程度后导电性的增加不明显.电荷掺杂形成了极子能级,明显降低了聚噻吩的前线轨道能隙、激发能和碳碳单双键键长交替,导电性增强.     

Nd掺杂对δ-MoN电子结构和输运性质的影响

为了探讨稀土掺杂对材料导电性影响的机理,采用密度泛函理论并结合非平衡格林函数方法,从理论角度研究了Nd掺杂δ-MoN的电子结构与输运性质,分别讨论了Nd取代Wyckoff坐标系中2a位置和6c位置的Mo原子时对δ-MoN导电性的影响.计算并分析了Nd掺杂δ-MoN的能带结构、态密度和伏安特性曲线.电子结构的计算结果表明,Nd掺杂使δ-MoN在费米能级附近的态密度增大,导致费米面电子出现的几率增加;伏安特性曲线显示Nd掺杂体系的电流大于未掺杂体系,说明Nd掺杂增强了δ-MoN的导电性,其中当Nd取代6c位置的Mo原子时δ-MoN的导电性增强较大.     

Co掺杂锐钛矿型TiO2可见光催化特性机理研究

基于密度泛函理论的平面波超软赝势,利用第一性原理对锐钛矿型TiO2及Co掺杂体系进行了电子结构和光学特性的模拟计算.结果显示,掺Co:TiO2的带隙降至1.55eV,新杂质能级的出现增强了光催化活性,电子发生跃迁的光波极限波长为800.5nm,相对介电函数虚部整体向低能方向移动,光吸收波长阈值为452.9nm.由此可见,Co掺杂锐钛矿TiO2后,确实改善了其光催化活性,并使受激波长范围由紫外红移至可见光区.     

聚噻吩掺杂性质的量子化学研究

采用密度泛函理论B3LYP方法,在6—31G基组水平下,对聚噻吩未掺杂体系及其掺杂体系进行了计算,根据几何、前线轨道和原子电荷的计算结果,分析了掺杂剂与聚噻吩链上极子异构区的作用．修正了以前研究工作中不考虑掺杂剂,而认为聚噻吩链上的电子得失是完全的这一缺欠．     

PDVT的电子结构、光谱及光学性质

有机共轭聚合物在电致发光材料上有较大的应用前景.采用密度泛函理论B3LYP方法在6-31 1++G(d,p)水平上计算了PDVT的分子结构和电子结构,并对红外光谱、净电荷布局等详细分析,结合前线轨道理论探讨了分子的稳定性和活性强弱.计算结果表明PDVT分子的环状结构共轭效应良好,其中C(26)的反应活性最高,最容易接受亲电试剂的进攻.前线轨道分析表明PDVT分子的内部环状结构对HOMO轨道做主要贡献,S原子对LUMO轨道做主要贡献,计算所得△Eg=0.489 eV表明它更倾向于接受电子并具有适合的能带宽度.PDVT分子具有较小的空穴重组能,空穴载流子速率大,可作为良好的空穴传输材料.     

基于DFT研究Ca2+取代对高岭石晶体结构及表面性质的影响

为探索Ca²⁺取代对高岭石晶体结构及表面性质的影响机制,构建了Ca²⁺取代高岭石晶胞模型,并采用密度泛函理论方法对其进行键长、键角、能带结构及态密度、前线轨道、Fukui指数及电荷等分析.模拟结果表明：取代后晶胞导电性增强,同时反应活性更强,其中Na⁺平衡构型比K⁺平衡构型更稳定;在(001)面及■面上,取代后高岭石表面反应活性增强,其中H1,O3位点反应活性增强,而水分子相较于■面更倾向于吸附在(001)面.结合表面电荷分布,取代高岭石(001)面电负性增强,同时Na⁺与(001)面及■面均以静电作用为主.Ca²⁺取代Al³⁺,使得晶体产生局部膨胀,周围晶格结构产生变化;同时取代后改变晶体轨道电子分布,轨道能量及电荷密度随之变化,最终改变反应活性.     

改性石墨烯纳米材料气敏特性的理论研究

利用基于密度泛函理论的第一性原理计算方法,研究单个CO和O2气体分子在多种金属原子修饰的石墨烯表面的吸附作用.结果表明,空位缺陷结构的石墨烯能够显著提高金属原子的稳定性,失去部分电荷的金属原子有助于调控气体分子的吸附特性.对比发现,单个金属Al和Mo原子掺杂的石墨烯体系对O2分子具有极高的灵敏性和选择性.通过不同气体分子的吸附能够调控石墨烯体系的电子结构和磁性.研究结果测试了不同金属原子修饰石墨烯表面的反应活性,为设计新型金属-石墨烯功能器件提供参考.     

CeO_2掺杂Mn的密度泛函理论

采用基于密度泛函理论的第一性原理方法,对不同Mn掺杂浓度的CeO2晶体结构进行了结构优化,分别计算了体相及掺杂后的晶胞参数,总能量,态密度和能带等.从理论上分析了Mn掺杂对CeO2晶体电子结构的影响,为CeO2材料的掺杂改性研究提供了理论依据.     

h-BN掺杂对金刚石晶体结构的影响

报道了在Fe70Ni30合金触媒和石墨系体中,掺杂六角立方氮化硼(h-BN)和硼(B)生长金刚石单晶的过程。研究发现,h-BN和B掺杂对于金刚石生长条件及形貌等具有较大的影响,其中h-BN掺杂生长金刚石的最低生长压力达到了6.2 GPa,同时晶体呈绿色条状。说明h-BN和B在金刚石晶体生长以及取代碳原子进入晶格时起到了不同的作用。通过X射线衍射及光电子能谱等表征手段,分析了硼氮对金刚石晶体结构的影响,以及硼氮在金刚石中的化学环境及成键方式。在此基础上阐述了硼氮掺杂的形成机制。     

空位和B、N、Al、P掺杂对Li在石墨烯上吸附的影响

采用基于密度泛函理论的第一性原理计算了空位和B、N、Al、P掺杂对Li在石墨烯上吸附的影响,结果表明:Li原子在完整石墨烯上吸附的稳定位置为心位,吸附高度在覆盖度低于1/40 ML时趋于恒值;B、N、P原子掺杂比Al掺杂石墨烯容易;杂质类型对Li在石墨烯上的吸附位置有显著的影响;空位和B、Al、P替位掺杂均加强了Li在石墨烯上的吸附,Al替位掺杂对Li在石墨烯上吸附的影响相对较大;Al、P掺杂改变了Li的稳定吸附位置(由心位移到顶位);Li在空位缺陷和N掺杂石墨烯上吸附后,两体系具有磁性,Li吸附在B-graphene、Al-graphene、P-graphene体系磁矩为零,不显示磁性。     

氟化碳化硅片的电子和磁性结构研究

通过密度泛函理论研究了氟化碳化硅片的电子结构和磁性特点,碳化硅中的硅原子被氟化,结果发现氟化的碳化硅片是带隙约为1.04eV的反铁磁半导体。通过简单的氟化,实现了材料由无磁性向反铁磁的转变,调节了材料的带隙,这预示着在未来的纳米功能材料中可能的应用。     

Road performances of mesoporous nano-silica modified asphalt binders

The objective of this paper was to find new modifier to improve the aging resistance and low temperature cracking resistance of asphalt. To investigate the aging resistance of modified asphalt binders, mesoporous nano-silica(doping Ti~(4+)) was used as a asphalt modifier. Some physical properties including penetration, ductility, and softening point of asphalt were analyzed with RTFO(Rotating thin film oven) aging and ultraviolet aging. Moreover, the performances of high and low temperature of modified asphalt binders with pressure aging were tested by dynamic shear rheometer(DSR) test and bending beam rheometer(BBR) test. These results showed that the penetration decreased, low temperature ductility, and softening point increased when adding mesoporous nano-silica to base asphalt. After ultraviolet radiation aging, the penetration loss and ductility loss of modified asphalt decreased than that of original asphalt, the increase of softening point was also significantly reduced than that of base asphalt. Furthermore, The test results of DSR and BBR showed that the G*sinδ and creep modulus‘s' of pressure aged asphalt decreased, but the creep rate ‘m' increased. It can be concluded that the aging resistance and cracking resistance of modified asphalt are improved by adding mesoporous nano-silica, especially the doping of Ti~(4+) could improve the aging resistance obviously.     

Electronic transport properties of cross graphene nano-junction

Graphene nanoribbons have special electrical properties, The electron transport properties can be regulated by controlling their geometry or doping. The metallic properties and semiconductor properties of different chiral graphene nanoribbons are used to build the cross graphene nano-junction in this paper. The method of density functional theory and non-equilibrium Green's function are used to research electronic transport properties of the graphene nano-junction with different heights and widths and locations of doping. It is shown that the graphene nano-junction shows metallic properties with increase in height and width of the arm. But the transmission spectral line has a clear oscillation. Since the doped nitrogen atom intensifies electron scattering, the electronic transport properties decrease. And the electron transport properties when the two arms are doped worsens more compared to the case of trunk doping.     

Functionalizations of boron nitride nanostructures

Boron nitride(BN) nanomaterials share the same atomic structures as their carbon counterparts, with mechanical and thermal properties second only to carbon counterparts. Especially, the iconicity of B-N bonds results in exceptionally high thermal stability and corrosion resistance, making BN nanomaterials a compelling contender for fabricating devices that can operate under harsh environments. However, all pristine BN nanomaterials are electric insulators and lack semiconductive functionality.How to efficiently regulate the electronic properties of BN nanomaterials has impeded the way of delivering their potential into applications. Here, we report an overview of key progress in functionalizing BN nanostructures by means of multi-physical-field coupling at nanoscale. In particular, we present how the chemical doping, electric fields, elastic strains and interfaces can modify the band structures and hence lead to narrowed bandgap and even magnetism in various BN nanostructures. We also discuss the effect of these modulation methods on charge carrier motility as well as potential challenges of their experimental implementation. Without applied doping, strain and electric field, employing inherent BN polarity to form electrically polarized interfaces is proposed to functionalize BN nanostructures towards controlled electronic properties combined with high carrier motility. We finally discuss recent progress of experimental synthesis of quality h-BN samples in large area.     

高温超导体中人工钉扎中心的种类与结构

提高高温超导体的临界电流密度是实现超导技术商业化发展性能与成本之间均衡的重要策略。在超导体中开发有效的纳米级人工钉扎中心是过去10年高温超导材料研究中的最大进展之一。从几何学的角度来说,超导体中的钉扎结构可以分为4类：零维钉扎中心、一维钉扎中心、二维钉扎中心和三维钉扎中心。对不同钉扎结构所产生的钉扎效果及其钉扎机制进行了系统的总结与阐述。经过对比分析得到了磁性材料掺杂效果比非磁性材料更好的结论,因此未来应该在磁性掺杂方面做更多的研究。     

Evaluation on High-temperature Adhesion Performance of Hot-applied Sealant for Asphalt Pavement

In order to investigate the high-temperature performances of the asphalt pavement hot-applied sealant, as well as to reduce failures of the sealant pullout, the softening point test and the flow test(two existing methods for evaluating high-temperature performances) were conducted. It was found that both tests could not accurately reflect the adhesion performances of the sealant at high temperatures. For this purpose, the adhesion test for PSAT(pressure sensitive adhesive tape) has been taken as a reference to develop a device that is suitable for evaluating the adhesion performances, by modifying relevant test parameters according to the road conditions at high temperatures. Thirteen common sealants were tested in the modified adhesion test, softening point test and f low test. The experimental results show that no significant correlation(p0.05) exists between the adhesion value, softening point, adhesion value and flow value; while a significant correlation(p0.05) exists between the softening point and flow value. The modified adhesion test is efficient in distinguishing the hightemperature adhesion performances of different sealants, and can be used as a standard method for evaluating such performances.     

合金元素Cu对α-Al2O3体结构拉伸强度和断裂性能影响的第一性原理研究

随着粉末冶金技术的发展,金属粉末被广泛用于金属-氧化铝基陶瓷复合材料的制备,具有提高烧结活性、增强增韧的作用。为了从原子尺度研究金属元素对氧化铝陶瓷结构的力学性能影响,采用基于密度泛函理论的第一性原理计算手段,建立合金元素Cu替代α-Al2O3中Al3+的掺杂晶胞模型与纯净α-Al2O3晶胞模型,通过第一性原理计算模拟拉伸试验方法（FPCTT）研究了二者的拉伸变形过程与断裂机制,该方法能够模拟晶胞沿单轴方向的理想拉伸变形过程。借助电荷密度分布图及差分图,Mulliken电荷布居分析等方法,从原子构型与电子结构方面研究了合金元素Cu对陶瓷材料α-Al2O3的影响作用与机理。研究发现：纯净α-Al2O3晶胞在应变为0.18时达到理论拉伸强度（55.51GPa）,并且伴随着Al原子向邻近的O原子层弛豫,具有明显的屈服效应。在合金元素掺杂模型中,由于Cu与O较弱的键合作用,变形过程伴随着Cu-O键的衰弱断裂,杂质体系在应变为0.12时发生断裂,拉伸强度为40.33GPa,其断裂方式为脆性断裂。结果表明：纯净的α-Al2O3结构单向拉伸变形过程伴随着较弱Al-O键的断裂且Al原子向O原子层弛豫,而合金元素Cu的进入基体结构后形成了键能更弱的Cu-O键,并在单向拉伸变形过程中率先断裂,导致体结构的断裂。说明合金元素Cu以原子替代方式进入α-Al2O3体结构中弱化了体结构的粘附性能,导致整体结构拉伸强度的降低。     

Diffusion process for efficiency improvement with high sheet resistance on traditional production lines of solar cell

By optimizing the diffusion temperature and time,four groups of samples with different sheet resistances are achieved.The front screen printing pattern and firing temperature are fine-tuned according to the needs.The performance of the low-and-plateau-temperature doping recipe(as recipe A)is better than that of the low-and-multiple-temperature doping recipe(as recipe B).And the 19.24%efficiency of volume production of monocrystalline solar cells with 238.95 mm2 and 80?/sq sheet resistance is obtained in the traditional process line.0.48%more efficiency is achieved than 60?/sq due to the reduction of the phosphorus surface doping and shallow junction by the low-and-plateau-temperature diffusion recipe.The module test shows that by using two drive-in zones,not only do we have a higher efficiency,but also have a stabler and lower power loss in encapsulation manufacture.It is showed that power of a large improvement will be gotten by statistical analysis and PC1D simulation.