Geometries and electronic structures of the hydrogenated diamond (100) surface upon exposure to active ions: A first principles study

To elucidate the effects of physisorbed active ions on the geometries and electronic structures of hydrogenated diamond films, models of HCO⁻₃ , H₃O⁺, and OH⁻ ions physisorbed on hydrogenated diamond (100) surfaces were constructed. Density functional theory was used to calculate the geometries, adsorption energies, and partial density of states. The results showed that the geometries of the hydrogenated diamond (100) surfaces all changed to different degrees after ion adsorption. Among them, the H₃O⁺ ion affected the geometry of the hydrogenated diamond (100) surfaces the most. This is well consistent with the results of the calculated adsorption energies, which indicated that a strong electrostatic attraction occurs between the hydrogenated diamond (100) surface and H₃O⁺ ions. In addition, electrons transfer significantly from the hydrogenated diamond (100) surface to the adsorbed H₃O⁺ ion, which induces a downward shift in the HOMO and LUMO energy levels of the H₃O⁺ ion. However, for active ions like OH⁻ and HCO⁻₃ , no dramatic change appears for the electronic structures of the adsorbed ions.     

Synthesis,Structure Characterization and Optical Properties of β Lithium Zinc Phosphate

β-LiZnPO_4 single crystal was successfully synthesized via hydrothermal method. It crystallizes in the trigonal space group R3 with a = b = 13.6490 ?, c = 9.1123 ?, γ = 120.00° and Z = 18. Structure of the crystal is constructed by LiO_4, ZnO_4 and PO_4 tetrahedral units to form a three-dimensional(3 D) framework. The crystal has a high transmission ranging from 350 to 800 nm with UV cut-off edge at 220 nm. The nonlinear optical efficiency of the as-prepared β-LiZnPO_4 is about 1.2 times as large as that of KDP(KH_2PO_4) standard. Additionally, band structure and density of states calculations for β-LiZnPO_4 were performed using the total-energy code CASTEP, based on density functional theory(DFT).     

助熔剂法生长非线性光学晶体Cd3Zn3B4O12及其性质研究

本文以PbO-0.25B2O3为助熔剂,利用顶部籽晶法获得了较大块的Cd3Zn3B4O12单晶.透过率测试结果显示该晶体的紫外截止波长位于310 nm处.利用Kurtz-Perry的方法对晶体的倍频效应进行了测试,结果显示该晶体的粉末倍频效应约为KDP的5倍,且能实现相位匹配.晶体的光损伤阈值约为840 MW(1064 nm,10 ns).该晶体的热分析结果显示Cd3Zn3B4O12晶体在熔点温度以上会产生分解,这也是阻碍高质量大块Cd3Zn3B4O12晶体生长最主要的因素.     

添加钴对HD制备NdFeB永磁体矫顽力的影响

采用X射线衍射分析(XRD)和BH测试仪分别研究了添加Co对HD制备的NdFeB永磁体微结构和磁性能的影响规律。微结构研究表明,添加Co前后的永磁体都由主要的四方相Nd2Fe14B(P42/mnm)和微量的富Nd相构成;但添加Co明显改变了永磁体的取向特性和磁性能;Horta法计算表明Co掺杂降低了Nd(FeCo)B永磁体的(004),(006)和(008)晶面的极密度因子;室温下磁性能测试表明,添加Co后永磁体矫顽力有了明显提升,从2038 kA.m-1提升到2162 kA.m-1,提高了接近124 kA.m-1;Kronm櫣ller-Plot行为研究表明两合金的矫顽力机理均为磁畴成核机制,由于Co添加同时增大了微磁参数αk和Neff,这增加磁畴反转需要的磁场能,从而提高了矫顽力。     

富勒烯在聚乙烯薄膜中的分散性研究

利用分子动力学方法,对纳米富勒烯/聚乙烯复合薄膜体系进行了模拟,分析了薄膜的空间限制作用、挤压作用以及薄膜变形速率对纳米粒子在聚乙烯薄膜中分散性的影响.结果表明,纳米复合薄膜的空间限制作用阻碍了纳米富勒烯的分散;对薄膜施加单向压力,纳米粒子受到的挤压作用可以促进纳米富勒烯的分散;在挤压变形量相同的条件下,薄膜变形的速率越小,纳米富勒烯的分散效果越好.当薄膜变形速率减小到一定程度时,富勒烯的分散效果能够接近其与聚合物本体进行复合的情形.     

线性离散系统谐强迫振动的电路定律分析方法

根据力学系统与电学系统物理量间的对应关系,提出了用电路定律处理线性离散系统谐强迫振动的方法。     

Dominant ferromagnetic coupling over antiferromagnetic in Ni doped ZnO: First-principles calculations

Frontiers of Physics - This article presents a review of our present understanding of the spin structure of the unpolarized hadron. Particular attention is paid to the quark sector at leading...