Vibrational Dynamics and Heat Capacity of Poly(3-methylthiophene): A Conducting Polymer

Using the Urey–Bradley force field and Wilson's GF matrix method as modified by Higgs, normal modes of vibration and their dispersions in poly(3-methylthiophene) have been obtained. They provide a detailed interpretation of its I.R. and Raman spectra. Characteristic features of the dispersion curves, such as regions of high density-of-states, repulsion, and character mixing of dispersive modes, are discussed. Predictive values of the heat capacity as a function of temperature have been calculated.     

三螺旋DNA分子poly(dT)·poly(dA)·poly(dT)的构型和振动谱

我们计算了ｐｏｌｙ（ｄＴ）·ｐｏｌｙ（ｄＡ）·ｐｏｌｙ（ｄＴ）的Ｈｏｗａｒｄ模型的原子笛卡尔坐标，并利用晶格动力学方法对模型进行了简正分析。结果发现其０ Ｐ ０对称振动模式位于８０４ｃｍ－１，这和８１０ｃｍ－１附近没有拉曼和红外谱线的实验结果不符。在８００～１０００ｃｍ－１的范围内只有四个振动模式，明显少于拉曼和红外光谱在该范围内的谱线数目。所以我们认为Ｈｏｗａｒｄ模型需要进一步地完善和修正，ｐｏｌｙ（ｄＴ）·ｐｏｌｙ（ｄＡ）·ｐｏｌｙ（ｄＴ）必须具有三条不完全一致的脊骨     

三螺旋DNA分子Poly(dT)·Poly(dA)·Poly(dT)碱基振动模式

利用晶格动力学方法计算了三螺旋 DNA分子 poly(d T)· poly(d A)· poly(d T)碱基振动模式 ,并根据势能分布矩阵对碱基振动模式进行了指定。计算的模式频率同拉曼光谱实验相符合     

Detecting the Rouse and Sub-Rouse Modes in Poly(Butyl Acrylate) and Poly(Ethyl Acrylate) Through Two-Dimensional Dynamic Mechanical Spectra

The difficulties of observing sub-Rouse modes (SRM) and Rouse modes (RM) in acrylate polymers has resulted in many arguments and disputes concerning the nature of their glass-rubber transition. Because different modes have different sensitivity to external perturbations, the two-dimensional dynamic analysis mechanical spectra (2D-DMS) was introduced to detect the local segments motion (LSM), SRM, and RM in poly(butyl acrylate) (PBA) and poly(ethyl acrylate) (PEA). The results of the asynchronous spectra showed the LSM, SRM, and RM of PBA and PEA are located, respectively, at about (?46 ～ ?29°C), (?28 ～ ?10°C), (?4 ～ 27°C), and about (?12 ～ ?5°C), (?3 ～ 6°C), and (10 ～ 44°C). Furthermore, the LSM and SRM of PBA and PEA have an overlap in the synchronous spectra. This is suggested to be caused by the higher coupling effect in PBA and PEA when compared with strong glass formation polymers, like polyisobutylene (PIB).     

Poly(dA)·poly(dT)结构的喇曼光谱和晶格动力学研究

我们成功地获得了溶液中poly(dA)·poly(dT)的喇曼光谱,并利用晶格动力学方法对于异规模型进行了简正分析.根据势能分布矩阵(PED)对每一个模式进行了指定.结果表明异规模型的简振频率和poly(dA)·poly(dT)的喇曼光谱符合得相当好,这说明溶液中的poly(dA)·poly(dT)完全有可能保留了固体纤维中的异规模型结构.     

EELS cross-section of surface phonons on Ag(001)

Summary We present EELS cross-section data of surface phonons on Ag(001) along . The inelastic intensity is due to the contribution of different modes which are not solved by the EEL spectrometer. However, the shape of the inelastic intensity shows a strong dependence on impact energy for all wave vectors, which allows tuning the EELS on the different modes. The dependence of the loss frequency on impact energy is at variance with the one reported previously for , leading to the conclusion that other modes contribute to the inelastic intensity besidesS ₁ andL ₁ which dominate at . In honour of Prof. Fausto Fumi on the occasion of his retirement from teaching.     

三链核酸poly(U)·poly(A)·poly(U)主链的振动位移

基于三链核酸 poly(U)· poly(A)·poly(U)的螺旋对称性 ,利用晶格动力学方法 ,计算了三链核酸分子 poly(U)·poly(A)·poly(U)主链振动的本征矢 ,探讨了振动位移矢量和线二色光谱的关系。结果表明 ,对应着磷酸双氧的反对称振动谱线可以用于直接确定磷酸根的取向 ,精度大约为 1°。其他谱线必须通过对分子的简正分析来帮助确定分子的结构。     

Infrared absorption spectra studies in (NaNO3–NaNO2) system

A complete infrared study of the mixed crystal system of NaNO₃ and NaNO₂ is carried out in the region 600—3000 cm^—1 at room temperature. The study includes fundamental internal normal vibrations of the NO^—₂ and NO^—₃ ions. The IR spectra, spectral band shape intensities, combination modes, and frequencies of the internal modes were studied as a function of NO^—₃ ion concentration. Special attention is paid to the bending mode, the combination mode, and a symmetric stretching mode.     

二甲基硅硼烷,o-(SiMe)_2B_(10)H_(10),振动光谱的理论研究

本文利用高斯 94从头计算程序在 6- 31 G基组下对二甲基硅硼烷 ,o- (Si Me) 2 B1 0 H1 0 ,进行几何优化及振动光谱的理论计算 ,并对主要谱带特性进行指认 ,结果与实验基本符合。振动模式分析表明 450 cm-1 以下的两个强带中 32 6cm-1 (计算值为 369cm-1 )似乎是两个 Si原子相对笼骨架中其余 B原子整体的伸缩振动 ,而 399cm-1 (计算值为 42 1 cm-1 )则为 Si- Si(及其联带的 C原子一起参与的 )对称伸缩振动。优化几何及振动光谱的研究表明重的杂原子硅占据二十面体硼笼骨架位置后使笼结构的刚性弱化     

固体核磁共振研究半晶聚-3-羟基丁酸酯和聚羟基丁酸戊酸酯的分子动力学

本文在150~370 K温度范围内,采用固体核磁共振（NMR）测定了半晶聚-3-羟基丁酸酯（PHB）,以及3-羟基戊酸酯单体质量分数分别为5%（PHBV5）和12%（PHBV12）的聚羟基丁酸戊酸酯共聚物在实验室坐标系和旋转坐标系条件下质子的自旋-晶格弛豫时间T₁和T_1ρ.通过弛豫时间随温度变化的理论拟合,分别获得上述半晶聚合物晶区和结晶区的分子动力学参数（包括E_a和τ₀）.这些结果从分子水平上阐述了PHB结构修饰和增强的原因.     

First principles study and comparison of vibrational and thermodynamic properties of XBi(X= In,Ga, B,Al)

In the present work, vibrational and thermodynamic properties of XBi(X = B, Al, Ga, In) compounds are compared and investigated. The calculation is carried out using density functional theory(DFT) within the generalized gradient approximation(GGA) in a plane wave basis, with ultrasoft pseudopotentials. The lattice dynamical properties are calculated using density functional perturbation theory(DFPT) as implemented in Quantum ESPRESSO(QE) code. Thermodynamic properties involving phonon density of states(DOS) and specific heat at constant volume are investigated using quasiharmonic approximation(QHA) package within QE. The phonon dispersion diagrams for InBi, GaBi, BBi, and AlBi indicate that there is no imaginary phonon frequency in the entire Brillouin zone, which proves the dynamical stability of these materials. BBi has the highest thermal conductivity and InBi has the lowest thermal conductivity. AlBi has the largest and GaBi has the smallest reststrahlen band which somehow suggests the polar property of XBi materials. The phonon gaps for InBi, GaBi, BBi and AlBi are about 160 cm~(-1), 150 cm~(-1), 300 cm~(-1), and 150 cm~(-1), respectively. For all compounds,the three acoustic modes near the gamma point have a linear behavior. C_V is a function of T~3 at low temperatures while for higher temperatures it asymptotically tends to a constant as expected.     

Vibrational spectra of thin eulytine films

This is a study of IR reflection spectra of systems of a thin Bi₄X₃O₁₂(X=Si, Ge) film and a substrate of fused quartz v-SiO₂ in the range 400–1600 cm⁻¹ at T=295 K. Bands assigned to Bi₄X₃O₁₂ are interpreted. It is found that single-photon processes are exhibited in the range 400–800 cm⁻¹, while biphonon processes, in the range 800–1600 cm⁻¹. I. Franko State University of Lvov, 50 Dragomanov St., 290005, Lvov, Ukraine. Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 64, No. 4, pp. 494–498, July–August, 1997.     

Vibrational properties of Cu nanowires

We have calculated local vibrational density of states (LDOS) of a center atom (CA) of a rectangular Cu nanowire with the axial orientation of 〈100〉, using a real space Green’s function approach with force constants extracted from interaction potentials based on the embedded atom method. The LDOS of a center atom of a strained nanowire is found to exhibit quite distinctive characteristics as compared to that of a strain-free nanowire, the most striking feature of which is the existence of high frequency modes above the bulk band even for small strain of 2.5%. We further find that these high frequency modes are shifted to even higher frequencies when the nanowire is exposed to an increasing axial strain.     

Heat capacity and phonons in poly(L-leucine)

Poly(L-leucine) is one of the polyamino acids having a bulky hydrophobic side-chain. For want of full phonon dispersion curves and density-of-states on this biopolymer Roleset al have interpreted their specific heat data in a limited way. In the present communication we report an analysis of the normal modes and their dispersion for poly(L-leucine) which leads to a very good agreement of the specific heat calculations with experimental measurements. It is observed that the main contribution to specific heat comes from the coupling of the back-bone skeletal and side-chain modes. Several other assignments have been revised. A special feature of some dispersion curves is their tendency to bunch in the neighbourhood of helix angle. It has been attributed to the presence of strong intramolecular interactions. Repulsion between the dispersion curves is also observed.     

三链DNA分子poly（dT）.poly（dA）.poly（dT）的低频振动模式

利用晶格动力学方法，首次计算了具有三螺旋结构的ｐｏｌｙ（ｄＴ）．ｐｏｌｙ（ｄＡ）．ｐｏｌｙ（ｄＴ）的低频振动模式，结果表明Ｗａｔｓｏｎ－Ｃｒｉｃｋ氢键的呼吸模式位于９０ｃｍ＾－＾１附近，而Ｈｏｏｇｅｎｓｔｅｅｎ氢键除了在９０ｃｍ＾－＾１附近存在模式外，还在更低频率上存在着几个更为强烈的呼吸模式，这一结果定性地解释了低盐度下ｐｏｌｙ（ｄＴ）．ｐｏｌｙ（ｄＡ）．ｐｏｌｙ（ｄＴ）的两步热融化。     

An Alternative Approach to the Classical Dynamics of an Extended Charged Particle

In this paper the analysis of the classical dynamics of a charged particle is carried out without considering that the electromagnetic field necessarily goes to zero at infinity. A quite general non-linear equation of motion is obtained for an extended charged particle valid for any distribution of charge in the particle and for an electromagnetic field satisfying any boundary conditions. Some common approximations are analyzed with detail to determine how the usual difficulties arise.     

Fluorescence Dynamics of DNA Condensed by the Molecular Crowding Agent Poly(Ethylene Glycol)

Condensation of extended DNA into compact structures is encountered in a variety of situations, both natural and artificial. While condensation of DNA has been routinely carried out by the use of multivalent cations, cationic lipids, detergents, and polyvalent cationic polymers, the use of molecular crowding agents in condensing DNA is rather striking. In this work, we have studied the dynamics of plasmid DNA condensed in the presence of a molecular crowding agent, polyethylene glycol (PEG). Steady-state and time-resolved fluorescence of the recently established condensation-indicating DNA binder, YOYO-1 [G. Krishnamoorthy, G. Duportail, and Y. Mely (2002), Biochemistry 41, 15277–15287] was used in inferring the dynamic aspects of DNA condensates. It is shown that DNA condensed by PEG is more flexible and less compact when compared to DNA condensed by binding agents such as polyethyleneimine. The relevance of such differences in dynamics toward functional aspects of condensed DNA is discussed.     

Thermoelectric Performance of Poly(3,4-ethylenedioxythiophene):Poly(styrenesulfonate)

Thermoelectric (TE) performances are systematically investigated for the pellets of poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) with different organic additives and heating process as organic TE materials. The electrical conductivity, Seebeck coefficient and thermal conductivity versus temperature are determined, respectively. It is found that there is no distinct change for the Seebeck coefficient among each sample with the additions of dimethyl sulfoxide and ethylene glycol. The thermal conductivity measured in a wide range of temperature indicates that the PEDOT:PSS pellet have an extremely low value. The highest figure of merit (Z_T= 1.75×10^-3) is observed at 270K among the PEDOT:PSS pellets.     

Investigation on the Heat Capacity of Water in Poly(Acrylic Acid)/Water Mixtures Through Stepscan Method

The heat capacity of poly(acrylic acid)/water mixtures with low water contents were measured by the stepscan differential scanning colorimetry (DSC) method and the C_p of the bound water in the mixtures were obtained based on simple equations with an assumption that the effect of interaction between polymer and water molecules could be ignored. The results indicated that the water decreased the glass transition temperature of poly(acrylic acid) (PAA), evidently as a plasticizer, and PAA/water mixtures were thermodynamically homogeneous blends. It was found that the C_p of nonfreezable water in PAA/water mixtures was higher than those of glassy water and cubic ice. The C_p increased with the water content, showing that average interactions between polymer and water decreased with water content. The C_p of bound water in the mixtures in the liquid state was lower than that of bulk water and also increased with water concentration, since the water molecules’ regular structures were broken. It showed that the C_p of bound water in the mixtures was lower than that of free water. The C_p of glassy water was calculated based on experimental C_p values of the PAA/water mixtures, which provided an easy way to obtain the C_p values of glassy water through a simple experiment. The values, however, were higher than those obtained by other researchers.