谐振子势阱囚禁玻色气体的玻色-爱因斯坦凝聚

基于Thomas-Fermi半经典近似方法研究了谐振子势阱约束下任意维理想玻色气体的玻色-爱因斯坦凝聚(BEC)．导出了玻色气体的BEC转变温度、基态粒子占据比例、内能和热容量等物理量的解析表达式,讨论了空间维度和谐振子势阱的影响．以二维和三维玻色系统为例,数值计算了上述热力学量,并与解析结果进行了对比,二者获得了较好的吻合．     

氩原子基态波函数和能量的解析计算

以第一性原理和变分原理为基础,给出了氩原子基态波函数的一种解析表达式,计算了基态氩原子(含类氩离子)的能量,导出了所涉及的所有积分的解析表达式.对氩原子,所得到的能量理论值与实验值的相对误差为0.22%.     

First passage percolation and escape strategies

Consider first passage percolation on with passage times given by i.i.d. random variables with common distribution F. Let be the time from u to v for a path π and the minimal time among all paths from u to v. We ask whether or not there exist points and a semi‐infinite path such that for all n. Necessary and sufficient conditions on F are given for this to occur. When the support of F is unbounded, we also obtain results on the number of edges with large passage time used by geodesics. © 2014 Wiley Periodicals, Inc. Random Struct. Alg., 47, 414–423, 2015     

Sulfur doping of AlN and AlGaN for improved n‐type conductivity

Achieving high levels of n‐type conductivity in AlN and high Al‐content nitride alloys is a long standing problem; significant decreases in conductivity are observed as the Al content is increased, a phenomenon that has been attributed to donors such as oxygen or silicon forming DX centers. We address this problem through a comprehensive first‐principles hybrid density functional study of potential n‐type dopants, identifying S_N and Se_N as two elements which are potential shallow donors because they do not undergo a DX transition. In particular, S_N is highly promising as an n‐type dopant because it also has a low formation energy and hence a high solubility. (© 2015 WILEY‐VCH Verlag GmbH &Co. KGaA, Weinheim)     

Synthesis,spatial structure and spectral properties of pyrylo‐4 (thio) squaraines variously substituted in cyclobutene moiety

Synthetic routes have been developed to a number of (thio) squaraine dyes containing the residues of CH‐acids at the central cyclobutene ring. The electronic and spatial structure as well as the chemical conversions and optical behaviour of the compounds obtained have been studied both theoretically and by X‐ray diffraction analysis, ¹H NMR and electronic spectroscopy. As shown, the electronic nature and sterical characteristics of the central ring substituents give rise to some general conformational features and crystal packing regularities and also govern the spectral position of the first π–π^* absorption band. The structure–property relationships established in the study provide guidance for the purposeful design of deeply coloured (thio) squaraines. Copyright © 2015 John Wiley & Sons, Ltd.     

Synthesis,crystal growth,structural, spectral,optical, thermal and dielectric studies of a new nonlinear optical material: 4-Hydroxy-l-proline-l-tartaric acid (1:1)

Single crystals of a new organic material, 4-hydroxy-l-proline-l-tartaric acid (HPTA) adduct, were grown by slow evaporation of an aqueous solution containing equimolar concentrations of 4-hydroxy-l-proline and l-tartaric acid at room temperature. Formation of new crystal has been confirmed by single crystal X-ray diffraction and NMR spectroscopic techniques. The single crystal XRD analysis shows that a molecule of 4-hydroxy-l-proline and a molecule of free l-tartaric acid both of which are interlinked to each other by two types of H-bonding interactions, namely O(6)–H(6)⋯O(2) and N(1)–H(1B)⋯O(10). The title compound (HPTA) crystallizes in monoclinic crystal system with non-centrosymmetric space group P2₁. The suitability of the crystal for optical applications was studied by UV–Vis–NIR spectroscopy. Fourier transform infrared (FT-IR) spectral analysis was used to confirm the presence of various functional groups in the grown crystals. The thermal stability of the compound was investigated by thermogravimetric and differential thermal analyses. The dielectric constant and dielectric loss of the crystal were studied as a function of frequency and temperature. The fluorescence spectral analysis of the title crystal shows an indigo emission. The second order nonlinear optical (NLO) property of the crystal was confirmed by the modified Kurtz–Perry powder second harmonic generation (SHG) test.     

Large Hexagonal Bi‐ and Trilayer Graphene Single Crystals with Varied Interlayer Rotations

Bi‐ and trilayer graphene have attracted intensive interest due to their rich electronic and optical properties, which are dependent on interlayer rotations. However, the synthesis of high‐quality large‐size bi‐ and trilayer graphene single crystals still remains a challenge. Here, the synthesis of 100 μm pyramid‐like hexagonal bi‐ and trilayer graphene single‐crystal domains on Cu foils using chemical vapor deposition is reported. The as‐produced graphene domains show almost exclusively either 0° or 30° interlayer rotations. Raman spectroscopy, transmission electron microscopy, and Fourier‐transformed infrared spectroscopy were used to demonstrate that bilayer graphene domains with 0° interlayer stacking angles were Bernal stacked. Based on first‐principle calculations, it is proposed that rotations originate from the graphene nucleation at the Cu step, which explains the origin of the interlayer rotations and agrees well with the experimental observations.     

Origin of pressure-induced insulator-to-metal transition in the van der Waals compound FePS3 from first-principles calculations

Pressure-induced insulator-to-metal transition (IMT) has been studied in the van der Waals compound iron thiophosphate (FePS₃) using first-principles calculations within the periodic linear combination of atomic orbitals method with hybrid Hartree–Fock-DFT B3LYP functional. Our calculations reproduce correctly the IMT at ∼15 GPa, which is accompanied by a reduction of the unit cell volume and of the vdW gap. We found from the detailed analysis of the projected density of states that the 3p states of phosphorus atoms contribute significantly at the bottom of the conduction band. As a result, the collapse of the band gap occurs due to changes in the electronic structure of FePS₃ induced by relative displacements of phosphorus or sulfur atoms along the c-axis direction under pressure.     

Photocontrolled Release of the Anticancer Drug Chlorambucil with Caged Harmonic Nanoparticles

While chemotherapy is one of the most used treatments in oncology, the systemic administration of chemotherapeutics generally results in undesired damages to healthy tissues and cells, side effects such as severe nausea and leukopenia, and reduced efficacy due to multidrug resistance and poor target accessibility. The limitations of conventional chemotherapy formulation have prompted the development of alternative nanomaterials-based strategies to achieve targeted and stimuli sensitive payload delivery to reach optimal local drug concentration at tumor sites. In this study, the anticancer drug chlorambucil (Clb) was conjugated to the surface of silica coated lithium niobate (LNO) harmonic nanoparticles (HNPs) using a photocaging tether based on coumarin-4-yl methyl derivative. Upon laser pulsed femtosecond irradiation at 790 nm, the second harmonic emission from the metal oxide core induced the efficient release of Clb, with concomitant contribution from the nonlinear absorption of the coumarin (CM)-based moiety.     

Ferromagnetism and structural deformation in monolayer alpha lead oxide induced by N and F doping: New insights from first principles

We study the structural, electronic, and magnetic properties of monolayer α-PbO_0.875A_0.125 (A = N, F), which are calculated using first principles. As a result, N doping induces local ferromagnetism centered at the N²⁻ site, originating from the spin-down N 2p valence states. On the other hand, F doping induces nonmagnetism and induces ab-plane deformation, where F⁻ receives one electron to its nearest-neighboring Pb^1.75+ ions. N doping redshifts the bandgap of the undoped system and transforms it to be indirect, while F doping blueshifts the bandgap through the Burstein-Moss effect. The hybridization of Pb 6p and O 2p orbitals is stronger near the A site than that of the crystal structure edge. Our result shows new insights, predicting possible experimental results for future functional device applications.