Ab initio calculations on the magnetism of small-sized metal clusters

金属团簇是团簇家族中的重要成员，在理论和实验方面都得到了广泛的研究。小的金属团簇通常能够表现出净磁矩，对于金属团簇的电子结构和磁性的研究可以更好的理解金属团簇的物理和化学特性。密度泛涵理论的发展就为物质的电子结构性质的理论研究打开了一个广阔的天地，提供了关键的方法步骤。本论文中采用了基于自旋极化的密度泛函理论的第一原理方法，对简单金属小团簇Aln(n=2-7)的磁性，重金属小团簇Wn(n=2-7)磁性，Al4团簇在NaCl（001）表面的结构和磁性进行了计算，主要内容包括： 1）对简单金属铝的小团簇Aln（n=2-7）的结构特性和磁性进行了理论计算。结果表明：团簇的结合能随着团簇中原子数的增...Metal clusters are important members of the cluster family, and many theoretical and experimental studies have been carried out on their properties. Small metal cluster usually shows magnetism. The study of the electronic structures and magnetism of metal clusters could help us understand the physical and chemical properties of metal clusters better. The development of density functional theory (D...学位：理学硕士院系专业：物理与机电工程学院物理学系_凝聚态物理学号：1982006115180

Al_4团簇在NaCl(001)表面的结构和磁性

利用第一次性原理计算Al4团簇的重心吸附在nACl表面上两种桥位,两种空位,在nA原子顶位及Cl原子顶位的结构、平均每个Al原子的吸附能、最低的Al原子和nACl(001)表面原子之间的距离和磁矩。结果表明,Al4团簇的重心吸附在nACl表面上nA的顶位是最稳定的结构,吸附能最大,总能最大,最低的Al原子和nACl(001)表面原子之间的距离最小,但团簇的磁矩为0μb,其他位置Al4团簇则保留其在自由空间的磁矩

Magnetism of Small-sized Al_n Clusters(n=2～7)

使用自旋极化的密度泛函理论下的第一原理方法,对简单金属铝的小团簇Aln(n=2～7)的结构特性和磁性进行了理论计算.结果表明:团簇的结合能随着团簇中原子数的增加而增大;虽然Al是简单金属,但是其小团簇Aln(n=2～7)具有磁性,磁矩在1μB和2μB间变化;通过能级图分析了Aln团簇磁矩的变化规律.此外,还分析了Aln团簇的磁矩、结合能、能量的一阶和二阶差分随原子数n的变化,讨论了最稳定团簇Al5的电子结构和电荷密度.The structural properties and magnetism of Aln small clusters(n=2~7) were studied by employing the first-principles calculations based on the spin-polarized density functional theory.The calculation results showed that:the binding energies increased with the number of atoms in the Alnclusters,although Al was a simple metal,the small-sized Aln clusters(n=2~7) could exhibit magnetism,with the magnetic moments changing between 1 μB and 2 μB.From the plot of energy levels,the magnetic moments of spin-polarized Aln clusters were discussed.Furthermore,the magnetic moment,the binding energy,the first and second differences of binding energies versus the number of atoms in the clusters were analyzed.The electronic structure and charge density of the most stable cluster Al5 were also discussed.国家自然科学基金(10774124,10702056)资

GaN基绿光LED芯片电流加速失效机理研究

采用电流加速的电应力老化方法研究GaN基绿光LED芯片的失效机理。LED芯片在经过60 mA电流老化424 h后,其发光效率总体趋势都是随老化时间增加而减小,但是小测量电流相比于大测量电流的发光效率衰减程度更为明显。同时,在正向偏压下电流电压曲线基本没有变化,而反向偏压下的反向电流随老化时间的增加而快速增加。笔者认为在电应力老化作用下,随老化时间增加,有源区的缺陷能级增多,在正向偏压下,缺陷能级起到一个有效陷阱的作用,增加了载流子的寿命,降低了辐射复合的几率,使得发光效率降低,但是并没有减小正向偏压下的电流,而反向偏压时,缺陷能级起到了一个漏电通道的作用,使得反向电流增大。福建省自然科学基金面上项目(2015J01655);;\n福建省教育厅基金项目(A类)(JA14025,JA13429)资助项

硅(100)衬底表面快速热退火制备硒纳米晶薄膜的结晶动力学

采用超高真空气相沉积系统在Si(100)衬底上制备非晶硒(Se)薄膜,然后快速热退火制得Se纳米晶薄膜。SEM观察结果表明,当热退火温度高于140℃,薄膜表面形貌从条状裂纹逐渐变成孤立的六角块状结构。Raman和XRD测试分析发现,退火后的Se纳米晶均为三角晶型结构,当退火温度高于140℃时,Se开始沿(100)方向择优取向结晶。分析得出,在Si(100)衬底上的Se晶粒(100)晶面的激活能比(101)晶面的激活能低,因而在(100)面上的结晶速率比(101)面上的结晶速率大,使得Se在(100)方向择优结晶。笔者认为这是因为Si(100)衬底对Se的结晶具有诱导作用,致使硒的结晶具有各向异性。福建省自然科学基金面上项目(2015J01655);;福建省教育厅基金项目(A类)(JA14025;JA13429);;华侨大学科研基金资助项目(12BS226

JUNO Sensitivity on Proton Decay p→νˉK+p\to \bar\nu K^+ Searches

The Jiangmen Underground Neutrino Observatory (JUNO) is a large liquid scintillator detector designed to explore many topics in fundamental physics. In this paper, the potential on searching for proton decay in $p\to \bar\nu K^+$ mode with JUNO is investigated.The kaon and its decay particles feature a clear three-fold coincidence signature that results in a high efficiency for identification. Moreover, the excellent energy resolution of JUNO permits to suppress the sizable background caused by other delayed signals. Based on these advantages, the detection efficiency for the proton decay via $p\to \bar\nu K^+$ is 36.9% with a background level of 0.2 events after 10 years of data taking. The estimated sensitivity based on 200 kton-years exposure is $9.6 \times 10^{33}$ years, competitive with the current best limits on the proton lifetime in this channel

JUNO sensitivity on proton decay p → ν K + searches*

The Jiangmen Underground Neutrino Observatory (JUNO) is a large liquid scintillator detector designed to explore many topics in fundamental physics. In this study, the potential of searching for proton decay in the $p\to \bar{\nu} K^+$ mode with JUNO is investigated. The kaon and its decay particles feature a clear three-fold coincidence signature that results in a high efficiency for identification. Moreover, the excellent energy resolution of JUNO permits suppression of the sizable background caused by other delayed signals. Based on these advantages, the detection efficiency for the proton decay via $p\to \bar{\nu} K^+$ is 36.9% ± 4.9% with a background level of $0.2\pm 0.05({\rm syst})\pm$$0.2({\rm stat})$ events after 10 years of data collection. The estimated sensitivity based on 200 kton-years of exposure is $9.6 \times 10^{33}$ years, which is competitive with the current best limits on the proton lifetime in this channel and complements the use of different detection technologies