检索结果-内蒙古大学图书馆

POLIR: Polarizable, flexible, transferable water potential optimized for IR spectroscopy

JOURNAL OF CHEMICAL PHYSICS 2008年第3期129卷 34504-1-34504-9页

作者： Mankoo, Parminder K. Keyes, Thomas Boston Univ Dept Chem Boston MA 02215 USA Johns Hopkins Univ Inst Computat Med Dept Biomed Engn Baltimore MD 21218 USA

A polarizable, flexible and transferable potential for water, POLIR, is presented. In addition to providing a good description of the usual structural and kinetic properties, POLIR correctly describes the vibrational frequencies, absolute infrared intensities, and HOH angle in clusters, liquid water, and ice, offering the possibility of a comprehensive classical theory of vibrational spectroscopy. The high degree of transferability suggests applications to solvation and to water that is confined, interfacial, and under the extreme conditions encountered in the geological and planetary sciences. (C) 2008 American Institute of Physics.

关键词： time-correlation function INCOHERENT NEUTRON-SCATTERING INSTANTANEOUS NORMAL-MODE ICE-IH 1ST PRINCIPLES INFRARED-SPECTROSCOPY MOLECULAR-DYNAMICS ENERGY SURFACE DIPOLE-MOMENT LIQUID WATER

来源：评论

学校读者我要写书评

暂无评论

IR and Raman spectra of liquid water: Theory and interpretation

引用

JOURNAL OF CHEMICAL PHYSICS 2008年第22期128卷 224511-1-224511-1页

作者： Auer, B. M. Skinner, J. L. Univ Wisconsin Inst Theoret Chem Madison WI 53706 USA Univ Wisconsin Dept Chem Madison WI 53706 USA

IR and Raman (parallel- and perpendicular-polarized) spectra in the OH stretch region for liquid water were measured some years ago, but their interpretation is still controversial. In part, this is because theoretical calculation of such spectra for a neat liquid presents a formidable challenge due to the coupling between vibrational chromophores and the effects of motional narrowing. Recently we proposed an electronic structure/molecular dynamics method for calculating spectra of dilute HOD in liquid D2O, which relied on ab initio calculations on clusters to provide a map from nuclear coordinates of the molecules in the liquid to OH stretch frequencies, transition dipoles, and polarizabilities. Here we extend this approach to the calculation of couplings between chromophores. From the trajectories of the fluctuating local-mode frequencies, transition moments, and couplings, we use our recently developed time-averaging approximation to calculate the line shapes. Our results are in good agreement with experiment for the IR and Raman line shapes, and capture the significant differences among them. Our analysis shows that while the coupling between chromophores is relatively modest, it nevertheless produces delocalization of the vibrational eigenstates over up to 12 chromophores, which has a profound effect on the spectroscopy. In particular, our results demonstrate that the peak in the parallel-polarized Raman spectrum at about 3250 wavenumbers is collective in nature. (c) 2008 American Institute of Physics.

关键词： ULTRAFAST INFRARED-SPECTROSCOPY INSTANTANEOUS NORMAL-MODE time-correlation function HYDROGEN-BOND DYNAMICS OH STRETCHING BAND VIBRATIONAL SPECTROSCOPY TEMPERATURE-DEPENDENCE LINE-SHAPES MOLECULAR-DYNAMICS DILUTE HOD

来源：评论

学校读者我要写书评

暂无评论

Nonequilibrium statistical operator in the generalized molecular hydrodynamics of fluids

引用

THEORETICAL AND MATHEMATICAL PHYSICS 2008年第1期154卷 75-84页

作者： Markiv, B. B. Omelyan, I. P. Tokarchuk, M. V. Natl Acad Sci Ukraine Inst Condensed Matter Phys Lvov Ukraine

We discuss the important role of the Zubarev nonequilibrium statistical operator method in the generalized molecular hydrodynamics of fluids. Using this method allows developing a consistent approach of generalized collective excitations for simple, ion, polar, magnetic, and some other fluids. We construct a nonequilibrium statistical operator and derive the corresponding transport equations for a system that relaxes and passes into the state of molecular hydrodynamics.

关键词： nonequilibrium statistical operator time-correlation function transport coefficient Liouville operator

来源：评论

学校读者我要写书评

暂无评论

The vibrational proton potential in bulk liquid water and ice

引用

JOURNAL OF CHEMICAL PHYSICS 2008年第15期128卷 54519-1-54519-20页

作者： Burnham, C. J. Anick, D. J. Mankoo, P. K. Reiter, G. F. Univ Houston Dept Phys Houston TX 77004 USA Harvard Univ McLean Hosp Sch Med Mailman Res Ctr Belmont MA 02478 USA Boston Univ Dept Chem Boston MA 02215 USA

We present an empirical flexible and polarizable water model which gives an improved description of the position, momentum, and dynamical (spectroscopic) distributions of H nuclei in water. We use path integral molecular dynamics techniques in order to obtain momentum and position distributions and an approximate solution to the Schrodinger equation to obtain the infrared (IR) spectrum. We show that when the calculated distributions are compared to experiment the existing empirical models tend to overestimate the stiffness of the H nuclei involved in H bonds. Also, these models vastly underestimate the enormous increase in the integrated IR intensity observed in the bulk over the gas-phase value. We demonstrate that the over-rigidity of the OH stretch and the underestimation of intensity are connected to the failure of existing models to reproduce the correct monomer polarizability surface. A new model, TTM4-F, is parametrized against electronic structure results in order to better reproduce the polarizability surface. It is found that TTM4-F gives a superior description of the observed spectroscopy, showing both the correct redshift and a much improved intensity. TTM4-F also has a somewhat improved dielectric constant and OH distribution function. It also gives an improved match to the experimental momentum distribution, although some discrepancies remain. (c) 2008 American Institute of Physics.

关键词： PATH CENTROID DENSITY TRANSFERABLE INTERACTION MODELS time-correlation function SELF-CONSISTENT-FIELD MOLECULAR-DYNAMICS SIMULATION INSTANTANEOUS NORMAL-MODE MOMENTUM DISTRIBUTION AB-INITIO NEUTRON-SCATTERING INFRARED-SPECTRUM

来源：评论

学校读者我要写书评

暂无评论

Induction model for molecular electrostatics: Application to the infrared spectroscopy of CO liquid

引用

JOURNAL OF CHEMICAL PHYSICS 2006年第20期124卷 204503,1-11页

作者： Mankoo, Parminder K. Keyes, Thomas Boston Univ Dept Chem Boston MA 02215 USA

Far-infrared intermolecular and midinfrared vibrational spectra of CO liquid have been calculated by Fourier transforming the quantum-corrected classical dipole correlation. The time dependence of the coordinates is determined from a standard nonpolarizable force field, and the dipole is determined from the coordinates with a "spectroscopic model" proposed herein. The model includes intramolecular induction and atomic charges, polarizabilities, and permanent dipoles. A good agreement with available experimental spectra is achieved. Our results demonstrate that the use of an anharmonic potential is necessary to reproduce the experimentally observed shift upon going from gas to liquid. The behavior of the simulated dipole time correlation functions suggests that CO liquid at 80 K exhibits aspects of both free rotation and solidlike caging. The proposition of some free rotation present in CO liquid supports Ewing's experimental hypothesis. (c) 2006 American Institute of Physics.

关键词： INSTANTANEOUS NORMAL-MODE time-correlation function GRADIENT-INDUCEDBIREFRINGENCE DIPOLE INTERACTION-MODEL CARBON-MONOXIDE ATOM POLARIZABILITIES QUADRUPOLE-MOMENTS DYNAMICS SPECTRA MYOGLOBIN

来源：评论

学校读者我要写书评

暂无评论

Identification of a wagging vibrational mode of water molecules at the water/vapor interface

引用

Physical Review E 2005年第5期71卷 050601(R)-050601(R)页

作者： Angela Perry Christine Neipert Christina Ridley Brian Space Preston B. Moore Department of Chemistry and Biochemistry University of the Sciences in Philadelphia Philadelphia Pennsylvania 19104 USA

An improved time correlation function description of sum frequency generation (SFG) spectroscopy was applied to theoretically describe the water/vapor interface. The resulting spectra compare favorably in shape and relative magnitude to extant experimental results in the OH stretching region of water. Further, the SFG spectra show a well-defined intermolecular mode at 875cm−1 that has significant intensity. The resonance is due to a wagging mode localized on a single water molecule. It represents a well-defined population of water molecules at the interface that, along with the free OH modes, represent the dominant interfacial species.

关键词： time-correlation function INSTANTANEOUS NORMAL-MODE FREQUENCY GENERATIONSPECTROSCOPY LIQUID WATER INFRARED-SPECTROSCOPY VAPOR INTERFACE SURFACE SPECTRUM DYNAMICS

来源：评论

学校读者我要写书评

暂无评论

Novel approaches in spectroscopy of interparticle interactions. Raman line profiles and dynamics in liquids and glasses

引用

JOURNAL OF MOLECULAR LIQUIDS 2004年第1-3期110卷 99-103页

作者： Kirillov, SA Natl Acad Sci Ukraine Inst Sorpt & Problems Endoecol UA-03142 Kiev 142 Ukraine Inst Technol & Informat Innovat UA-03134 Kiev 134 Ukraine

A novel fitting, method implemented recently in vibrational spectroscopy of disordered systems is briefly overviewed. It enables modelling of real line profiles intermediate between Lorentzian and Gaussian by an analytical function which has an analytical counterpart in the time domain. Numerous applications of this theoretical approach are discussed. (C) 2003 Elsevier B.V. All rights reserved.

关键词： vibrational spectra liquids amorphous solids line profile time-correlation function

来源：评论

学校读者我要写书评

暂无评论

New applications of an old theory - The Rouse theory - in polymer dynamics and viscoelasticity

引用

JOURNAL OF THE CHINESE CHEMICAL SOCIETY 2002年第5期49卷 629-638页

作者： Lin, YH Natl Chiao Tung Univ Dept Appl Chem Hsinchu 300 Taiwan

As recently shown by a close agreement between the calculated and measured viscoelastic spectra of a binary blend solution over a wide frequency range, the quantitative validity of the Rouse theory is discussed, pointing out why the traditional way of testing by a single parameter - the viscosity - is misleading. A "bird's-eye" view of the Rouse theory in relation to various aspects of polymer dynamics and viscoelasticity is shown. This represents a fresh way of looking at some of interrelations between fundamental problems in chain dynamics. This paper illustrates the application potential of the Rouse theory by reviewing the research schemes that make use of the well-tested theory to elucidate two fundamental problems : (1) onset of entanglement and (2) the motions associated with a single Rouse segment. It is shown that through careful designs of research, analyses in terms of the Rouse theory can provide vitally important and informing results.

关键词： polymer viscoelasticity polymer dynamics Rouse theory Rouse segment Gaussian chain depolarized photon-correlation spectroscopy entanglement Monte-Carlo simulation time-correlation function

来源：评论

学校读者我要写书评

暂无评论

Structure and dynamics of the branched polysaccharide scleroglucan in dilute solutions studied by 1D and 2D NMR spectroscopy

引用

CARBOHYDRATE POLYMERS 2001年第4期46卷 349-363页

作者： Vlachou, S Politou, A Dais, P Mazeau, K Taravel, FR Univ Crete Dept Chem NMR Lab Iraklion 91409 Crete Greece Univ Grenoble 1 CNRS Ctr Rech Macromol Vegetales CERMAV F-38041 Grenoble 9 France

Variable temperature and magnetic field dependent C-13 NMR relaxation measurements (T-1 and NOE) were carried out for the branched polysaccharide scleroglucan in DMSO-d(6) dilute solutions. The relaxation data of the backbone carbons were analyzed quantitatively by using the bimodal time-correlation functions developed by Dejean, Laupretre, and Monnerie (DLM), which offered the best quantitative description of the segmental motion of the carbohydrate chains. Simple internal rotations of the free hydroxymethyl groups of the backbone rings about the exocyclic C-5-C-6 bonds superimposed on segmental motion have been described as a diffusion process of restricted amplitude. Multiple internal rotations involving the exocyclic hydroxymethyl group of the ring at the branched point and that of the side chain ring, as well as the side chain ring itself were described by employing a composite TCF for side chain motions superimposed on polymer segmental motions. These time-correlation functions and their Fourier transform pairs, the spectral densities, offered the best interpretation of the relaxation data of the exocyclic free hydroxymethyl groups, and the pendent D-glucorynosyl ring. Finally, the H-1- and C-13 NMR spectra of the neutral scleroglucan in DMSO-d(6) were analyzed by employing a series of 2D NMR experiments. The 500 MHz H-1 NMR spectrum of scleroglucan at 283 K show severe peak overlaps, which do not allow the complete assignment of all signals in the carbon spectrum. (C) 2001 Elsevier Science Ltd. All rights reserved.

关键词： scleroglucan time-correlation function spin-lattice relaxation

来源：评论

学校读者我要写书评

暂无评论

time-correlation function for periodically-forced nonlinear stochastic system

引用

COMMUNICATIONS IN THEORETICAL PHYSICS 1998年第3期30卷 397-404页

作者： Li, JH He, KF Huang, ZQ Nanjing Univ Dept Phys Nanjing 210008 Peoples R China Beijing Normal Univ Inst Low Energy Nucl Phys Beijing 100875 Peoples R China

The equilibrium time-correlation function for a general cosine-forced stochastic system are calculated respectively by the perturbation theory and the linear response theory. The results obtained by the two theories are basically identical. By calculation rye find that it has two terms. One is the original time-correlation function (in the case when the external signal does not exist). The other is caused by the perturbing external signal. The two terms have the same relaxation time, and the latter has oscillator behavior.

关键词： perturbation theory linear response theory time-correlation function relaxation time

来源：评论

学校读者我要写书评

暂无评论

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案：

请选择收藏分类：

通借通还

建议与咨询 留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

时间限定

文献类型

馆藏选择

核心期刊

语言

文献类型

帮助

文字说明：

检索规则说明：

检索范例：

分类表

所选分类

限定检索结果

文献类型

馆藏范围

日期分布

学科分类号

主题

机构

作者

语言

请选择保存的检索档案： 新增检索档案 确定 取消

请选择收藏分类： 新增自定义分类 确定 取消

通借通还

建议与咨询留下您的常用邮箱和电话号码，以便我们向您反馈解决方案和替代方法

请选择保存的检索档案：

请选择收藏分类：