Showing papers by "Peter J. Rossky published in 2001"
TL;DR: In this paper, the structure of the binary dense CO2−water interface at 20 MPa and 318 and 338 K and 28 MPa/ 318 K was investigated by molecular dynamics computer simulations.
Abstract: We report the results on the structure of the binary dense CO2−water interface at 20 MPa and 318 and 338 K and 28 MPa and 318 K, as investigated by molecular dynamics computer simulations. Realistic potential models are used to describe the interactions, and the Ewald summation technique is employed to account for the long range electrostatic interactions. It is shown that the interface is molecularly sharp with distortions from a flat interface due to the presence of capillary waves induced by thermal fluctuations. The use of a local dynamic interface definition1 provides a revealing density profile in which interfacial packing of fluids on both sides of the interface is observed. Atomic radial distribution functions, orientational probability distribution functions, and H-bond analysis are used to probe the nature of the bulk to interface transition. Specific attractive interactions between CO2 and water due to Coulombic interactions are evident. The interfacial tension is determined from the pressure t...
94 citations
TL;DR: In this article, the authors showed that defects leading to tetrahedral kinks in the polymerization direction that were proposed previously to explain the optical anisotropy of polymer films are indeed energetically stable.
Abstract: Quantum chemical analyses of poly(p-phenylenevinylene) (PPV)-based polymers with conformational and chemical defects are presented. It is shown that defects leading to tetrahedral kinks in the polymerization direction that were proposed previously to explain the optical anisotropy of polymer films (Hu et al. Nature 2000, 405, 1030) are indeed energetically stable. These defects are shown not to affect the primary electronic absorption band, but they may localize the electron−hole excitation in one segment of the polymer chain.
72 citations
TL;DR: In this article, the electronic structure of the betaine dye molecule, pyridinium-N-phenoxide [4-(1-pyrinio)phenolate] including the effects of geometry and polar solvents, has been studied at an ab initio level using the reference interaction site model self-consistent field (RISM-SCF) method.
Abstract: The electronic structure of the betaine dye molecule, pyridinium- N-phenoxide [4-(1-pyridinio)phenolate] including the effects of geometry and polar solvents, has been studied at an ab initio level using the reference interaction site model self-consistent-field (RISM-SCF) method. Acetonitrile (CH3CN) and water (H2O) were selected as polar solvents. We obtain both the optimized solute geometry in solution and the total free energy profile with respect to variation in the torsion angle between the pyridinium and phenoxide rings and analyze the various electronic and solvation contributions. The betaine molecule in the gas phase has a twisted geometry, which is slightly more twisted in solution. In acetonitrile, the calculated structure shows good agreement with earlier semiempirical results for the minimum free energy structure. It is shown that the solute dipole moment is strongly enhanced in polar solution, also in accord with earlier semiempirical calculations. However, in solution, there is relatively ...
48 citations
TL;DR: In this article, the instantaneous normal mode (INM) method is implemented in the context of mixed quantum-classical molecular dynamics simulations and applied to the analysis of the short-time solvation dynamics of the hydrated electron.
Abstract: The instantaneous normal mode (INM) method is implemented in the context of mixed quantum-classical molecular dynamics (MD) simulations and applied to the analysis of the short-time solvation dynamics of the hydrated electron. Numerically suitable equations for computing the solvent dynamical matrix (Hessian) for both ground and excited adiabatic electronic states are derived using analytical derivative methods of quantum chemistry. Standard diagonalization of the Hessian leads to the sets of eigenfrequencies and eigenvectors that underlie the INM theory. Comparison of the hydrated electron and pure water INM spectra and the corresponding mode participation ratios shows that the quantum solute enhances the participation of collective low-frequency unstable modes (imaginary frequencies) at the expenses of stable ones. Distinct differential INM spectra, involving distinct solvent configurational averages, are introduced to describe the changes experienced by the solvent INMs upon the vertical excitation of ...
42 citations
TL;DR: In this article, a molecular dynamics investigation of the electronic decoherence rate for electron transfer (ET) in a solvated protein molecule is presented, and it is shown that decoherent occurs on an ultrafast time scale of 2.4 fs, considerably faster than fluctuations in the electronic coupling.
33 citations
TL;DR: In this paper, molecular dynamics simulations have been used to examine the effect of supercritical water solvent density on the competition between reaction pathways for the dissociation step of a model SN1 reac...
Abstract: Molecular dynamics simulations have been used to examine the effect of supercritical water solvent density on the competition between reaction pathways for the dissociation step of a model SN1 reac...
32 citations
TL;DR: Prezhdo et al. as mentioned in this paper evaluated the suitability of the combined mean-field/surface hopping (MF/SH) algorithm for simulation of realistic chemical envirgences.
Abstract: To evaluate the suitability of the combined mean-field/surface hopping (MF/SH) algorithm (Prezhdo, O. V.; Rossky, P. J. J. Chem. Phys. 1997, 107, 825) for the simulation of realistic chemical envir...
31 citations
TL;DR: In this paper, the authors report the results of simulations of the ionic mobility of Na+ and Cl- in supercritical water at 673 K, including solvent densities below those previously considered in simulation or experimental data, and find that spatially inhomogeneous solvation structure around the ions and solvent dynamics are strongly coupled in determining transport rates.
Abstract: We report the results of simulations of the ionic mobility of Na+ and Cl- in supercritical water at 673 K, including solvent densities below those previously considered in simulation or experimental data. By considering these results along with earlier published analyses, we find that the spatially inhomogeneous solvation structure around the ions and solvent dynamics are strongly coupled in determining transport rates. The appearance of a plateau in the infinite-dilution conductivity over a wide range of intermediate solvent densities is a result of a subtle balance of excess (dielectric) friction and a nonlinear variation in the viscous friction. The result is strongly influenced by the inhomogeneous solvent density around the ions, but cannot be rationalized on the basis of only structural criteria. A reduced effective ionic radius is introduced that is inversely proportional to the Walden product and can be trivially evaluated from experimental conductivity results. It is shown that when represented i...
30 citations
TL;DR: In this paper, a method based on centroid molecular dynamics (CMD) was proposed to calculate nonlinear quantum force correlation functions important in the golden rule approach for studying vibrational energy relaxation (VER) in condensed phases.
Abstract: We present a method based on centroid molecular dynamics (CMD) to calculate nonlinear quantum force correlation functions important in the golden rule approach for studying vibrational energy relaxation (VER) in condensed phases. We consider a model of a diatomic molecule in a two-dimensional neon liquid and also a diatomic coupled to a small Helium cluster. The predictions of the theory for the neon bath are compared and found in close agreement with available theories for VER based on the Egelstaff correction factor and Feynman–Kleinert variational theory. For the Helium cluster, the force spectrum obtained from CMD is found to be in slightly better agreement with the exact result than a method based on a cumulant approach. The results support the use of CMD in condensed phase studies of VER when quantum effects are important.
28 citations
19 citations
TL;DR: Within the framework of Feynman-Kleinert variational theory, simple equations for correlation functions of arbitrary nonlinear operators are derived and extended to longer times by a well established ansatz.
Abstract: Within the framework of Feynman–Kleinert variational theory, simple equations for correlation functions of arbitrary nonlinear operators are derived. These correlation functions, meaningful only for short times, are extended to longer times by a well established ansatz. The approach is tested against exact results for the quantum force correlation function in a two-dimensional Helium cluster problem and is found to perform very well. The theory is also applied to calculate quantum force correlation functions for a diatomic in a larger Neon bath. The results indicate that the method is effective for vibrational energy relaxation processes in simple liquids when quantum effects are significant.
TL;DR: In this article, the ability of centroid molecular dynamics (CMD) to determine quantum correlation functions pertinent to the bath force correlation function, appearing in the rate expression for vibrational energy relaxation, was investigated.
TL;DR: In this article, the impact of electronic decoherence on electronic dynamics and electron transfer reactions in particular, in condensed phase environments is discussed, and analytical expressions are considered for a common model system in which ET occurs between relatively displaced harmonic surfaces.
TL;DR: Ultrafast observations of fluid interfaces show that the way molecules interact at these junctions is both structurally and dynamically different from interactions in the bulk liquid.
Abstract: Ultrafast observations of fluid interfaces show that the way molecules interact at these junctions is both structurally and dynamically different from interactions in the bulk liquid