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  • 1
    Electronic Resource
    Electronic Resource
    Theoretical study for the excited states of MoO4−nS2−n (n=0∼4) and MoSe2−4 (1990)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 93 (1990), S. 1865-1875 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Ground and excited states of six molybdenum complexes, MoO4−nS2−n (n=0∼4) and MoSe2−4, are systematically studied by symmetry adapted cluster (SAC) and SAC-CI theories. In the ground states, the ionicity of MoO2−4 is much larger than those of MoS2−4 and MoSe2−4. The calculated electronic spectra compare well with the observed spectra. New systematic assignments of the spectra are given. Most of the peaks are assigned to the electron-transfer type transitions from ligands to the metal. Many assignments are different from the previous ones. The observed relationships in the electronic spectra of these complexes are examined and corrected. The solvation effect is argued briefly.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459064
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  • 2
    Electronic Resource
    Electronic Resource
    Crack-Healing Behavior of Si3N4/SiC Ceramics under Cyclic Stress and Resultant Fatigue Strength at the Healing Temperature (2002)
    Westerville, Ohio : American Ceramics Society
    Journal of the American Ceramic Society 85 (2002), S. 0 
    Details
    ISSN: 1551-2916
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Si3N4/SiC composite ceramics were sintered and subjected to three-point bending. A semi-elliptical surface crack of 100 μm surface length was made on each specimen. The crack-healing behavior under cyclic stress of 5 Hz, and resultant cyclic fatigue strengths at healing temperatures of 1100° and 1200°C, were systematically investigated. The main conclusions are as follows: (1) Si3N4/SiC composite ceramics have an excellent ability to heal a crack at 1100° and 1200°C. (2) This sample could heal a crack even under cyclic stress at a frequency of 5 Hz. (3) The crack-healed sample exhibited quite high cyclic fatigue strength at each crack-healing temperature, 1100° and 1200°C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1151-2916.2002.tb00446.x
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  • 3
    Electronic Resource
    Electronic Resource
    Translational and orientational dynamics of a water cluster (H2O)108 and liquid water: Analysis of neutron scattering and depolarized light scattering (1995)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 102 (1995), S. 3566-3579 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Molecular dynamics simulations were performed to analyze effects of the translational and orientational motions on the coherent and the incoherent neutron scattering and the depolarized light scattering (DLS) spectra of the water cluster (H2O)108 and liquid water. In the neutron scattering of the water cluster and liquid water, there exist two modes, the high and the low frequency modes, in the collective longitudinal current fluctuations for oxygen atoms. The low frequency mode is almost independent on wave number above 0.6 A(ring)−1, while the velocity of the high frequency mode is faster than 3000 m/s, as experimentally observed in liquid water. The nature of this high frequency mode is analyzed by changing the molecular interaction parameters characterizing the hydrogen bond structure of the system. It was found that the high frequency mode is very sensitive to hydrogen bond structure and a three dimensional network structure of the hydrogen bonds is essential for its existence. In order to characterize the water dynamics reflected in the neutron scattering, the density fluctuations of water are classified into two kinds of dynamics; the local oscillatory dynamics around local potential minima (intrabasin dynamics) and the large amplitude dynamics associated with the structure change of hydrogen bond network (inherent structure transitions; interbasin dynamics). We also analyzed the collective and individual longitudinal current fluctuations for hydrogen atoms.For the depolarized light scattering, the contribution of the cross correlation is examined and compared with those in the collective orientational relaxation in the far infrared spectrum. The interaction-induced component plays a dominate role below 300 cm−1 while the permanent component does above 300 cm−1 in DLS of the cluster and liquid water. The induced component relaxes very slowly in the cluster and yields almost an identical relaxation to that of the dipole–dipole interaction tensors. It was found that the power spectrum of the DLS base line of liquid water obtained from the molecular dynamics calculation is in good agreement with experimentally observed spectrum by Walrafen et al. © 1995 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.468580
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  • 4
    Electronic Resource
    Electronic Resource
    Instantaneous normal mode analysis of liquid water (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 100 (1994), S. 6672-6683 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present an instantaneous-normal-mode analysis of liquid water at room temperature based on a computer simulated set of liquid configurations and we compare the results to analogous inherent-structure calculations. The separate translational and rotational contributions to each instantaneous normal mode are first obtained by computing the appropriate projectors from the eigenvectors. The extent of localization of the different kinds of modes is then quantified with the aid of the inverse participation ratio—roughly the reciprocal of the number of degrees of freedom involved in each mode. The instantaneous normal modes also carry along with them an implicit picture of how the topography of the potential surface changes as one moves from point to point in the very-high dimensional configuration space of a liquid. To help us understand this topography, we use the instantaneous normal modes to compute the predicted heights and locations of the nearest extrema of the potential. The net result is that in liquid water, at least, it is the low frequency modes that seem to reflect the largest-scale structural transitions. The detailed dynamics of such transitions are probably outside of the instantaneous-normal-mode formalism, but we do find that short-time dynamical quantities, such as the angular velocity autocorrelation functions, are described extraordinarily well by the instantaneous modes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.467027
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  • 5
    Electronic Resource
    Electronic Resource
    Dynamics and relaxation of an intermediate size water cluster (H2O)108 (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 6063-6075 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The potential surface, melting, surface structure, and hydrogen bond network of an intermediate size water cluster (H2O)108 are investigated. The orientation relaxations of single molecule and of collective molecules are analyzed and compared with those of liquid water. The collective orientation relaxation (COR) (i.e., dielectric relaxation) of the water cluster is found to be much faster than that of liquid water due to different boundary conditions. In both liquid and cluster, the cross correlation between individual molecular dipoles plays an important role in static and dynamic quantities. COR of the cluster yields a so-called 1/f fluctuation in contrast to the well-known Debye relaxation in liquid water. In order to understand these differences of COR between the water cluster and liquid water, the wave vector dependence of the transverse and longitudinal components of COR is examined. A surface effect on hydrogen bond network and the correlation between structural change and coordination number are analyzed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.467321
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  • 6
    Electronic Resource
    Electronic Resource
    Third order nonlinear response of liquid water (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 106 (1997), S. 4889-4893 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Third order nonlinear response of liquid water is investigated by using a classical molecular dynamics simulation. The calculated response function yields a marked agreement with the recent experimental results. The physical origins of the third order spectrum is analyzed in terms of the translational and the librational motions. Its temperature dependence and isotope effect are also analyzed. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.473538
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  • 7
    Electronic Resource
    Electronic Resource
    Dynamics of proton attachment to water cluster: Proton transfer, evaporation, and relaxation (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 6358-6366 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: A proton attachment dynamics to a water cluster is investigated by using a classical molecular dynamics calculation. It is found that three dynamical stages are involved: (1) ultrafast (∼10−14 s) proton attachment to a water molecule of the cluster which followed by (2) the fast (∼10−13 s) sequential proton transfer over several water molecules on the cluster surface and then, (3) the gradual (∼10−11 s) proton penetration to the cluster core. In the first two stages, the large kinetic energy of the order of hundreds kcal/mol is released to the system, which results in the evaporation of a few water molecules from the cluster. The water molecules evaporating in these early stages have large vibrational and translational energies. The mechanism of the energy relaxation and the proton transfer in each process are investigated. The large amplitude vibrational motion promotes sequential concerted proton exchange transfers in the earlier stages (1) and (2). The precise configurational matching of the hydrogen bond coordination and the O–O distance fluctuation are the most important factors to determine the direction and the rate of the proton transfer in the stage (3). © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.472488
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  • 8
    Electronic Resource
    Electronic Resource
    Mechanism of fast proton transfer in ice: Potential energy surface and reaction coordinate analyses (2000)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 9090-9100 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The mechanism of proton transfer in ice is investigated theoretically by examining the potential energy surfaces and determining the reaction coordinates. It is found to be quite different from that in liquid water. As shown by many authors, proton transfer in liquid water is promoted by the structure fluctuation, creating three-coordinated water molecules in the hydrogen bond network rearrangement, and the excess proton makes transitions among these three-coordinated water molecules as forming a so-called Zundel structure, (H5O2)+. This kind of large structural rearrangement cannot take place in ice. Nevertheless, the proton transfer in ice can be very fast. It is found that the strong constraint on the molecular geometry in ice is the source of the facile proton transfer. This constraint reduces the stabilization of the excess proton state in two ways: (1) as O–O cannot shrink freely, it cannot form a stable Zundel structure in which two water molecules share the excess proton locating at the center of the shortened O–O bond, and (2) as the existence of the repulsive force, an Eigen structure cannot be much stabilized. This repulsive force also contributes to partially shorten the O–O distance and thus facilitating a proton transfer. As the result, the excess proton is not trapped in a deep energy minimum but makes the transfers on small energy barriers. The molecular geometry relaxation along the proton transfer is analyzed; it is found that O–O stretchings/shrinkages at the excess proton moiety are mutually coupled to assist the sequential proton transfers in a concerted fashion. The energetics and geometrical changes along these reaction coordinates are analyzed. The potential energies are found to be fairly flat for different locations of the excess proton. The nature of the excess proton solvation from the surrounding water molecules are analyzed; it is shown that the solvation by even distant shells yields a significant contribution to the potential energy surface of the proton transfer. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1319636
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  • 9
    Electronic Resource
    Electronic Resource
    Fluctuation, relaxation and rearrangement dynamics of a model (H2O)20 cluster: Non-statistical dynamical behavior (1997)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 106 (1997), S. 3329-3337 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Relaxation phenomena in a model (H2O)20 cluster are investigated by considering energy fluctuations and dielectric relaxation, making connections with the underlying hydrogen-bond rearrangement dynamics. In particular, we relate these effects to the potential energy surface, including rearrangement mechanisms, minimum energy pathways and normal mode excitations. The statistical behavior of structural transitions in this water cluster is also examined. The transition rates estimated from RRKM theory are compared with those obtained by molecular dynamics (MD) simulations. The RRKM rates are 1–3 orders of magnitude larger than the MD values and the difference is larger at low energy. To find the origin of this discrepancy, the mechanism of coupling among various modes is examined. We find that there is significant coupling only among a subset of the normal modes in the low energy dynamics. A modified statistical theory, assuming that only a subset of modes contributes to the reaction rate, reproduces the energy dependence of the MD transition rates quite well. It is also found that the energy fluctuations and dielectric relaxation are non-Debye in character, and instead exhibit so-called 1/f spectra. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.473081
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  • 10
    Electronic Resource
    Electronic Resource
    Off-resonant fifth-order nonlinear response of water and CS2: Analysis based on normal modes (1998)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 108 (1998), S. 240-251 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Off-resonant fifth-order nonlinear response functions of liquid water and liquid CS2 are analyzed based on two normal-mode schemes, quenched and instantaneous normal modes. It was found that the fifth-order response function is very sensitive to the mode mixing in polarization, arising from the quadratic term of polarization with respect to the different modes. The echo signal is drastically reduced by this off-diagonal mode mixing in polarization even without any rapid frequency modulation mechanism. The near absence of echo signal thus obtained for liquids is consistent with the recent experimental results for liquid CS2. The present calculation yields the different fifth-order signals for different polarization geometries, as experimentally shown by Tokmakoff and Fleming [J. Chem. Phys. 106, 2569 (1997)]. The mode mixing dynamics is investigated in terms of the bispectra of total potential energy and polarizability. © 1998 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.475375
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