Theoretical investigation on the electronic structure,elastic properties,and intrinsic hardness of Si₂N₂O

According to the density functional theory we systematically study the electronic structure, the mechanical prop- erties and the intrinsic hardness of Si2N2O polymorphs using the first-principles method. The elastic constants of four Si2N2O structures are obtained using the stress-strain method. The mechanical moduli (bulk modulus, Young’s mod- ulus, and shear modulus) are evaluated using the Voigt-Reuss-Hill approach. It is found that the tetragonal Si2N2O exhibits a larger mechanical modulus than the other phases. Some empirical methods are used to calculate the Vickers hardnesses of the Si2N2O structures. We further estimate the Vickers hardnesses of the four Si2N2O crystal structures, suggesting all Si2N2O phases are not the superhard compounds. The results imply that the tetragonal Si2N2O is the hardest phase. The hardness of tetragonal Si2N2O is 31.52 GPa which is close to values of β-Si3N4 and γ-Si3N4.     

2H-PbI2晶体的电子结构和力学性质

采用基于密度泛函平面波赝势方法(PWP)方法,计算了六角晶系2H-PbI2晶体的电子结构、力学性质和硬度。采用局域密度近似(LDA)方法计算的晶格常数、带隙、弹性常数与实验值和理论值符合较好。计算表明,2H-PbI2是一种直接带隙的半导体,带隙大约为2。38eV。运用复杂晶体硬度计算公式计算了六角晶系2H-PbI2晶体的硬度,硬度值大约为2. 54 GPa。还发现2H-PbI2晶体的各向异性非常明显。     

过渡金属掺杂ZnO的电子结构和光学性质

利用基于密度泛涵理论的超软赝势法(USPP)，结合局域密度近似(LDA)，对过渡族金属离子掺杂的纤锌矿型ZnO做第一性原理计算，得到了它的平衡晶格常数、结合能、电子态密度分布、能带结构、介电函数、光学吸收系数等性质，详细讨论了掺杂后ZnO化合物的电子结构及成键情况，并结合实验结果定性分析了掺杂后光学性质的变化. 关键词： 氧化锌 掺杂 第一性原理 光学性质     

锶原子共振滤波器内部光子转换效率的研究

详细研究了温度及氩稀有气体压力对锶原子共振滤波器有效的内部光子转换效率的影响。证明了内部光子转换效率随氩气压的增加而增加,在温度的变化关系中存在着最佳温度值。     

Theoretical investigation on the electronic structure,elastic properties, and intrinsic hardness of Si2N20

According to the density functional theory we systematically study the electronic structure, the mechanical prop- erties and the intrinsic hardness of Si2N2O polymorphs using the first-principles method. The elastic constants of four Si2N2O structures are obtained using the stress-strain method. The mechanical moduli （bulk modulus, Young’s mod-ulus, and shear modulus） are evaluated using the Voigt-Reuss-Hill approach. It is found that the tetragonal Si2N2O exhibits a larger mechanical modulus than the other phases. Some empirical methods are used to calculate the Vickers hardnesses of the Si2N2O structures. We further estimate the Vickers hardnesses of the four Si2N2O crystal structures, suggesting all Si2N2O phases are not the superhard compounds. The results imply that the tetragonal Si2N2O is the hardest phase. The hardness of tetragonal Si2N2O is 31.52 GPa which is close to values of β-Si3N4 and γ-Si3N4.     

2H-PbI_2晶体的电子结构和力学性质

采用基于密度泛函平面波赝势方法(PWP)方法,计算了六角晶系2H-PbI2晶体的电子结构、力学性质和硬度.采用局域密度近似(LDA)方法计算的晶格常数、带隙、弹性常数与实验值和理论值符合较好.计算表明,2H-PbI2是一种直接带隙的半导体,带隙大约为2.38eV.运用复杂晶体硬度计算公式计算了六角晶系2H-PbI2晶体的硬度,硬度值大约为2.54GPa.还发现2H-PbI2晶体的各向异性非常明显.     

Effects of dispersion and filtering induced by periodic multilayer mirrors reflection on attosecond pulses

Using temporal and spectral methods,the effects of dispersion and filtering induced by Mo/Si multilayer mirrors reflection on incident attosecond pulses were studied.First,two temporal parameters,the pulse broadening factor,and the energy loss factor,were defined to evaluate the effects of dispersion and filtering.Then,by analyzing these temporal parameters,we investigated and compared the dispersion and filtering effects on attosecond pulses.In addition,we explored the origins of pulse broadening and energy loss by analyzing the spectral and temporal characteristics of periodic Mo/Si multilayer mirrors.The results indicate that the filtering effect induced by Mo/Si multilayer mirrors reflection is the dominant reason for pulse broadening and energy loss.     

腹部彩超联合CA125诊断卵巢浆液性肿瘤的研究

本研究探讨腹部彩超联合糖类抗原125(CA125)诊断卵巢浆液性肿瘤的价值。选取卵巢浆液性肿瘤患者80例,其中卵巢浆液性囊腺瘤患者23例,浆液性交界性肿瘤患者30例,浆液性癌患者27例,比较各组超声特征及血清CA125差异。浆液性交界性肿瘤、浆液性癌患者囊实性回声、有血流分布、腹水比例明显高于卵巢浆液性囊腺瘤患者(P<0.05),形态规则、边界清晰比例明显低于卵巢浆液性囊腺瘤患者(P<0.05);浆液性癌患者血清CA125为(301.45±104.42)U/mL,明显高于浆液性交界性肿瘤和卵巢浆液性囊腺瘤患者(P<0.05);浆液性交界性肿瘤患者血清CA125为(210.10±98.28)U/mL,明显高于卵巢浆液性囊腺瘤患者(P<0.05);超声联合血清CA125诊断浆液性癌的特异性、准确率和阳性预测值分别为90.57%、87.50%和81.48%,明显高于超声检查(P<0.05)。腹部彩超联合CA125鉴别诊断卵巢浆液性肿瘤有较好的价值。     

一种新型金属配合物的非线性光学特性的研究

利用单光束Z扫描技术，在波长532nm、脉宽8ns的条件下研究了新型的金属有机配合物ECuCl2（BOEP）2]的三阶非线性光学性质。由实验结果发现配位化合物虽然没有明显的非线性吸收性质，但是其三阶非线性折射率比相应配体大很多。探讨了配合物的结构和其三阶非线性光学性质的关系，认为配位化合物的丌共轭离域体系的增大和金属中心离子与配体之间的电子转移是配合物具有更大非线性折射率的主要原因。选择具有π键的配体与金属离子合成为配合物，使其非线性效应明显增强，这对合成性能更好的非线性材料有一定的参考价值。     

γ-Si3N4在高压下的电子结构和物理性质研究

采用基于密度泛函平面波赝势方法(PWP)和广义梯度近似(GGA-PW91),计算了不同压强下γ-Si3N4的电子结构、光学性质和力学性质.基于计算结果,分析讨论了γ-Si3N4各物理参数随外压力的变化规律.计算表明,γ-Si3N4是一种适合于在高压条件下工作的材料.