B和N原子掺杂超长(3,3)单壁碳纳米管的从头算研究

用从头算的周期边界条件方法,建立了(3,3)型超长单壁碳纳米管的新模型.使用B3LYP/3-21G方法计算了B和N掺杂纳米管的结构参数、掺杂能量、能带结构以及能隙.研究表明,B和N原子掺杂的(3,3)型单壁碳纳米管具有直接带隙半导体特征,其α轨道计算所得能隙值分别为1.797和2.041 eV.     

Study on the morphology of lithium formate monohydrate (HCOOLi·H2O) crystal by the Periodic Bond Chain theory

The theoretical growth morphology of Lithium Formate Monohydrate (LFM) had been derived by means of the Periodic Bond Chain (PBC) theory and compared to that of synthetic crystals. From this derivation, the surface anisotropy factors ξ_hkl for the different faces were obtained. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

股权激励、经理人异质性与控制权私利

文章探讨了不同类型的经理人对股权激励与控制权私利之间关系所起的作用,并以2008~2018年所有A股上市公司数据进行验证,结果发现:独立型经理人对股权激励抑制控制权私利的行为起着正向调节作用,依附型经理人并未发挥有效的监督效应;在内部控制质量较低的环境中,股权激励对控制权私利的抑制效应更显著,发挥的替代效果更佳。本文的研究深化了对经理人公司治理角色的认识,拓宽了对控制权私利的研究。     

Nonequilibrium molecular dynamics simulation for studying the effect of pressure difference and periodic boundary conditions on water transport through a CNT membrane

A NEMD simulation system is constructed to simulate at two-dimensional (2D) periodic boundary conditions (PBCs) and to create two different pressures on two sides of the carbon nanotube (CNT) membrane. The simulation results show that water permeation through the same CNT membrane driven by different pressure differences exhibit similar transport phenomenon including unusually fast water permeation and a periodic (non-parabolic) radial velocity distribution unlike the parabolic form characteristic of continuum flow in the CNT membrane. A three-dimensional (3D) PBC system is also constructed to simulate water permeation through the same CNT membrane at the same pressure differences, to show the effect of PBC and simulation methodologies on transport phenomenon. The two systems both show that the forward/backward water flux increases/decreases with increasing the pressure difference from 1.0 MPa to 8.0 MPa. However, the net flux is higher for the 3D PBC system, especially at higher pressure difference is high. In general, the NEMD simulation method using the 2D PBC system is shown to be a feasible and valuable tool for studying pressure-driven permeation processes such as nanofiltration through these studies with model CNT membrane.     

Structure of 2-(2-(anthracen-9-ylmethylene)hydrazinyl)-4-(3-methyl-3-phenylcyclobutyl)thiazole by combined X-Ray crystallographic and molecular modelling studies

A single crystal of 2-(2-(anthracen-9-ylmethylene)hydrazinyl)-4-(3-methyl-3-phenylcyclobutyl)thiazole (C₂₉H₂₅N₃S) containing anthracene, thiazole and cyclobutane rings has been synthesised. The synthesised crystal structure was characterised using IR, ¹H-NMR and ¹³C-NMR spectroscopic and X-Ray analysis techniques. In the crystal, neighbouring molecules formed chains along [110] by interconnecting with N–H···N hydrogen bonding and π–π interactions. The geometrical parameters of the title compound were optimised by Gaussian 09 software in the gas phase and Quantum-Espresso software under Periodic Boundary Conditions (PBC) in the solid phase. Theoretically, IR, NMR spectra, Mulliken, NPA and AIM atomic charges, Hirshfeld surface and frontier molecular orbitals (FMOs) of the title compound were examined. Using the Hirshfeld surface and two-dimensional (2D) fingerprint graphics, the presence of intermolecular interactions in the crystal packing were analysed. The energies of these interactions and their distribution on the crystal structure were shown graphically. In general, it was seen that theoretical calculations were consistent with X-Ray results.     

B、N原子掺杂超长扶手椅型碳纳米管的GTOs-PBC方法研究

使用密度泛函B3LYP/3-21G*方法,并用周期边界条件模型,计算了B、N掺杂纳米管的结构参数、掺杂能量、能带结构和能隙.研究表明,碳纳米管掺杂B、N原子后,能隙均增大,变为半导体.B原子掺杂的碳纳米管具有直接带隙,而N原子掺杂则具有间接带隙,B掺杂的(6,6)和(9,9)管以及N掺杂的(6,6)和(9,9)管的能隙...     

超长(n,n)型碳纳米管的密度泛函理论研究

用密度泛函B3LYP/3-21G(d)方法,并利用周期边界条件,研究了n=2—20不同管径的超长(n, n)型单壁碳纳米管的结构、能量、能带结构和能隙.结果表明,管径和能量(或生成焓)都随n有很好的变化规律,并可拟合成很好的解析函数.当n为2和3时,碳纳米管的能隙分别为1.836eV和0.228eV,呈半导体特征,且具有间接带隙;当n=4—20时,能隙介于0.027 eV和0.079 eV之间,呈较强的金属性,且具有直接带 关键词： 扶手椅型碳纳米管 周期边界条件(PBC) 超长模型 能带     

Oxidative Nuclear Bromination of Substituted 4-Pyridones Using Pyridinium Bromochromate

An alternative convenient approach for the bromination of various poly-substituted 4-pyridones has been developed via an oxidative nuclear bromination in the presence of sole pyridinium bromochromate (PBC). The PBC performs the dual role of oxidant and source of Br⁺ during the process.

[Supplementary materials are available for this article. Go to the publisher's online edition of Synthetic Communications® for the following free supplemental resource(s): Full experimental and spectral details.]