Phase Transition Studies in Some 4-n-Alkyl-N-(4-n-Alkyloxy-Benzylidene)-Anilines

The results of phase transition investigations in two homologous series of 4-n-alkyl-N-(4-n-alkyloxy-benzylidene)-anilines, viz., 60. m and 70. m compounds using thermal microscopy, differential scanning calorimetry, density and refractive index measurements are reported. The nature of the order of various phase transitions and the pre-transitional effects in the fluctuation dominated non-linear regions in the vicinity of IN, IA and NA transitions are discussed in the light of the available data on other nO. m compounds.     

Studies on Induced Smectic Phases (II) Transition Enthalpies,X-ray Patterns and Layer Spacings of Orthogonal Phases of Binary Mixtures of Nematogens with Contrasting Dielectric Anisotropies

Binary mixtures of two nematogens, 4,4′-di-n-heptyl-azobenzene with 4-n-pentyl-4′ -cyano biphenyl were studied by optical, calorimetric and X-ray measurements. At a given concentration induced phases with a sequence S_A, S_B, S_E were detected, the properties of which were discussed.     

Studies of Image Processing and Refractive Index in Blue Phase

The isotropic - blue phases - cholesteric phase transitions are studied in a thermotropic (COC) by image processing and refractive index measurements. Textures of blue phases are optically characterized as well as their transition points. The experimental investigation employed here is sensitive to detect changes in the structural configuration of blue phases as a consequence of our refractive index data. In this context the experimental results are presented and discussed.     

纤锌矿和岩盐结构ZnO的相变、弹性性质和电子结构研究

采用基于密度泛函理论框架下的第一性原理平面波超软赝势(USP)方法,结合广义梯度近似(GGA)计算了岩盐结构(B1)和纤锌矿结构(B4)ZnO的相变、弹性性质,并分析了B1和B4相ZnO在相变点处的电子结构特征.计算结果表明:ZnO在12.72 GPa时发生了由B4相向B1相的转变.B1和B4相ZnO的体弹性模量分别为171.5 GPa和132.8 GPa.能带结构的结果表明B1相是间接带隙半导体,带隙值为1.404 eV,而B4相是直接带隙半导体,带隙值为1.107 eV.     

(Sr0.7Bi0.2)TiO3取代BNT基无铅陶瓷的相变及储能特性

采用弛豫铁电体(Sr0.7Bi0.2)TiO3与铁电体(Bi0.5Na0.5)TiO3构建了的新型二元系BNT基无铅陶瓷材料:(1-x)(Bi0.5Na0.5)TiO3-x(Sr0.7Bi0.2)TiO3(记为BNT-xSBT,x=10mol;、20mol;、30mol;和40mol;).通过传统固相法进行制备,研究了(Sr0.7 Bi0.2)TiO3取代对其结构、相变、铁电性能和储能特性的影响.结果表明,室温所测BNT-xSBT陶瓷为准立方结构;介温和铁电性则证实其为极性三方和非极性四方共存相结构.A位复合占位的BNT-xSBT陶瓷是典型的弛豫铁电体,其Tm随x的增大而减小.低温(Td)处的介电反常源于结构(三方和四方)起伏所引起的缓慢转变过程.(Sr0.7 Bi0.2)TiO3取代量增大时,其Td降低,四方相增多,并伴随非极性微区增长;并导致BNT-xSBT陶瓷的铁电性减弱和电滞回线变形.x=30mol;时,BNT-xSBT陶瓷具有大的Pmax=26.8μC/cm2、小的Pr=1.4μC/cm2,和较好的储能特性:W=0.74 J/cm3,η=68.5;(@70 kV/cm).     

Comparison of the crystal structure and molecular models of N,N-diisobutyl-2-(octylphenylphosphinyl)acetamide (CMPO)

The crystal structure of N,N-diisobutyl-2-(octylphenylphosphinyl)acetamide, or CMPO was recently determined. The compound crystallizes in the space group P2₁/c witha=13.446(6),b=22.280(7),c=17.217(7) Å, =92.07(4)°, andD _calc=1.05 g/cm³ forZ=8 @20°C). Molecular mechanics, molecular dynamics, and MNDO calculations were also performed on CMPO utilizing the SYBYL¹ suite of programs. The results from these calculations are compared to the crystal structure and to similar calculations performed on CMPO using ALCHEMY^2,3. In general, the results from the calculations agree fairly well with the parameters from the crystal structure.     

Superconducting Transition of (TMTSF)2CLO4 in Magnetic Fields

Abstract

Superconducting transition of (TMTSF)₂ClO₄ was studied by conductivity measurements along the most conductive a-axis in magnetic fields applied along three different principal crystallographic axes. The GL coherence lengths at OK along the a-, b-, and c*-axes, ?_a(0)≈ 600A, ?(0) ≈ 540A, and ?_c*(0) ≈ 60A were obtained from the measurements of the temperature dependence of the upper critical field H_C2 near the transition temperature. The anisotropy is discussed in terms of the dimensionality arising from the crystal structure and of the conductivity anisotropy in the normal state.     

Phase Characterization,Enthalpies and Entropies of Transition,of Five Substituted N-(1-Biphenylethylidene) Benzylamines

Five N-(1-biphenylethylidene) benzylamines expressed by the general formula C₆H₅C₆H₄C(CH₃) = N-CH₂-C₆4HX (X = H, m-F, m-Cl, M-Br and p-OCH₃) were synthesized and their thermal behavior studied within the temperature range of -75 to 250°C.

The solid-liquid, liquid-solid transition temperatures were recorded with a DSC analyzer and the thermodynamic parameters ΔH_m and ΔS_m were estimated. A relationship between these parameters and the molecular weigth was found. The compound m-fluoro N- (1-biphenylethylidene) benzylamine showed an l_i → l_n transition at 341.5°K, which was better observed by cooling the sample at 10°C/min. The liquid crystal behavior was confirmed by cross polarized microscopy.     

Phase Formation and Structure of (RE,M)2Ca0.5Sr0.5Cu2O6+δ (RE=La,Pr, M=Ca,Sr)

The samples of (RE,M)₂Ca_0.5Sr_0.5Cu₂O_6+d are prepared by solid state reaction method. The single phase boundary of RE and M in (RE,M)₂Ca_0.5Sr_0.5Cu₂O_6+d is 1.0 ∼2.0 and 0 ∼1.0 respectively. In (Pr,M)₂Ca_0.5Sr_0.5Cu₂O_6+d, the phase boundary of Sr is 0 ∼1.0. The structure of (RE,M)₂Ca_0.5Sr_0.5Cu₂O_6+d belongs to the structure type of 212 cuprate superconductors with space group I4/mmm.     

Molecular Vibration Analysis of lonicity and Phase Transition in TMPD-TCNQ (1:1) Charge Transfer Salt

The infrared spectra of the (1:1) charge transfer salt of N, N, N′, N ‘-tetramethyl-p-phenylendiamine (TMPD) with 7, 7, 8, 8-tetracyanoquinodimethane (TCNQ) and with fully deuterated TCNQ are reported. The assignment of the vibrational data is obtained on the basis of the comparison with that of neutral and ionized parent molecules; additional relevant information is extracted from the low temperature (～15 K) infrared and Raman spectra. The vibrational analysis leads one to estimate for TMPD-TCNQ a degree of ionicity of 0.9₂, which corresponds to an almost fully ionic ground state. The interpretation of the vibrational data has been carried out in the light of an appropriate model for the electron-molecular vibration interaction in regular or dimerized mixed stack charge transfer complexes. The study of the temperature dependence of the infrared spectra of TMPD-TCNQ confirms that the already known phase transition at about 220 K is likely associated with a transition from a regular to a dimerized mixed stack.     

高压对Ti2AlX(X=C,N)结构、弹性和电子性质的影响

采用第一性原理方法,对比研究了Ti2AlC和Ti2AlN在高压下的结构、弹性和电子性质.结果表明,Ti2 AlC和Ti2AlN的品格常数a、c和体积V均随着外压的增大减小,但二者变化规律略有不同,都体现了材料的各向异性.通过对弹性常数、体模量、剪切模量、杨氏模量等弹性性质的分析,发现它们均随外压的增加而增大,并验证了Ti2AlC和Ti2AlN在0～50 GPa范围内的力学稳定性.此外,还从电子态密度的角度考察了Ti2AlC和Ti2AlN的电子性质,认为它们均具有共价键和金属键的双重特性,并发现在0 ～ 50 GPa范围内压力对态密度影响较小.本文计算结果与已有实验值和理论值吻合较好.     

单层MXene纳米片Ti2N电磁特性的过渡金属(Sc、V、Zr)掺杂效应

二维材料MXene纳米片由于具有较大的比表面积和较高的电子迁移率而受到广泛的关注。本文采用基于密度泛函理论的第一性原理计算,对单层MXene纳米片Ti₂N电磁特性的过渡金属(Sc、V、Zr)掺杂效应进行了系统研究。结果表明,所有过渡金属掺杂体系结合能均为负值,结构均稳定;其中Ti₂N-Sc体系的形成能为-2.242 eV,结构更易形成,且保持稳定;掺杂后Ti₂N-Sc、Ti₂N-Zr体系磁矩增大;此外,Ti₂N-Sc体系中保留了较高的自旋极化率,达到84.9%,可预测该体系在自旋电子学中具有潜在的应用价值。     

Phase transformation in the system TlBi(Te1‐xSex)2

TlBiTe₂ and TlBiSe₂ ‐ that are ternary analogs of the IV‐VI semiconductors ‐, although they crystallize in the same space group R m (D⁵_3d), exhibit different behaviour during heating. The observed phase transformation depends on Se content (x) in the system TlBi(Te_1‐xSe_x)₂ and the transformation disappears by increasing Se content after a certain value (x = 0.25). This dependence is examined through the analysis of the DSC non‐isothermal measurements and an attempt for the explanation of the observed behaviour is undertaken through the consideration of off‐center atoms. (© 2004 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)     

A Spectroscopic Study of the Second Order Phase Transition in Bis (p-toluene sulfonate) Diacetylene Polymer Crystals

The second order phase transition at 195 K which occurs in bis (p-toluene sulfonate) diacetylene polymer crystals has been studied by optical reflection and transmission, Raman and far-infrared spectroscopy. Order parameter fitting to the data suggests that at low temperatures the transition has a two dimensional character while closer to the transition it appears to be three dimensional. There are indications of a broad transition region which might be expected for a predominately two dimensional phase transition in which fluctuations dominate the behaviour of the system. Analysis of new X-ray crystallographic data gives some support to a structural model in which the transition would have a substantial two dimensional character.     

Molecular structure,DFT studies,Hirshfeld surface analysis,energy frameworks,and molecular docking studies of novel (E)-1-(4-chlorophenyl)-5-methyl-N′-((3-methyl-5-phenoxy-1-phenyl-1H-pyrazol-4-yl) methylene)-1H-1, 2, 3-triazole-4-carbohydrazide

Abstract

The synthesis of the compound and its crystal structure having a monoclinic crystal system has been reported earlier. Optimized bond lengths and angles are showing good agreements with experimental data using DFT/B3LYP method. Energy of highest occupied molecular orbital and lowest unoccupied molecular orbital has been predicted to analyze the stabilities of compound. Crystal explorer 17.5 helps to visualize intermolecular interactions and its contributions to each interaction within molecule. The preeminence of dispersion energy component over the other components was established by interaction energy calculations and lattice energy framework analysis using same software. The molecular docking study was performed for molecule using AutoDock software.     

Microstructure and phase transformation of Ti3AC2 (A = Al,Si) in hydrofluoric acid solution

In this paper, Ti₃AC₂ (A = Al, Si) were prepared by pressureless argon shielding synthesis technique. The microstructure and phase transformation of as‐prepared Ti₃AC₂ (A = Al, Si) in hydrothermal hydrofluoric acid (HF) solution were investigated systematically. Results showed that the obtained Ti₃AlC₂ and Ti₃SiC₂ were closely aligned layered structure. In hydrothermal HF solution, Al or Si element was preferentially etched from the layered structure, inducing obvious transformation of microstructure and phase composition. For Ti₃AlC₂, Al atoms diffused out of the structure and reacted with HF to form AlF₃•H₂O, which induced the rearrangement of the Ti and C atoms, and finally resulted in the formation of TiC_x cubic phase. With the hydrothermal temperature and reaction time increasing, the TiC_x phase gradually disappeared and the grain size of AlF₃•H₂O gradually increased. When Ti₃SiC₂ was immersed in hydrothermal HF solution, the main products were TiC and SiC. Interestingly, with the hydrothermal treatment temperature and reaction time increasing, TiC gradually disappeared, while SiC nearly kept unchanged. This can be explained that SiC was covalently bonded carbide, while TiC was metallically bonded, having relatively weak bond energy and consequently being unstable in hydrothermal HF solution.     

RbCdF3:Ni2+晶体结构相变、光谱精细结构和EPR谱的研究

本文采用半自洽场(semi-SCF)3d轨道模型和μ-κ-α模型,利用完全对角化方法,建立了Oh、D4h对称晶体场局部结构参数与光谱精细结构、EPR谱之间的定量关系,统一解释了RbCdF3∶Ni2+晶体的光谱精细结构和EPR谱。所得理论结果与实验值符合很好。     

The crystal and molecular structures of two bromo bis(N,N-dipropylthiocarbamoyl) sulfidocopper(I) complexes

The reaction of copper(I) bromide, CuBr, with the tetraalkylthiurammonosulfides R₄tms (R = ⁱPr, ⁿPr) affords the copper(I) complexes ⁱPr₄tmsCuBr (I) (C₁₄H₂₈BrCuN₂S₂, orthorhombic, Pna2₁, Z = 4, a = 12.487(2), b = 12.699(2), c = 12.742(2) Å) and ⁿPr₄tmsCuBr (II) (C₁₄H₂₈BrCuN₂S₃, monoclinic, P2₁/n, Z = 4, a = 9.092(5), b = 23.408(11), c = 10.082(7) Å, = 104.90(5)°), which exist in the solid as monomeric units featuring three-coordinate copper(I). The ligands are bidentate and coordination is completed by the bromine atoms. The configurations of the six-membered metal-ligand ring in (I) and (II) are more severely distorted than the previously reported structurally related complexes of ethyl series. The crystal structural studies are complemented and confirmed by IR and ¹H-NMR spectroscopies, as well as room temperature, magnetic, solution conductivity, and molecular weight studies.