Response to “Comment on ‘A centroid molecular dynamics study of liquid para-hydrogen and ortho-deuterium’ ” [J. Chem. Phys. 122, 057101 (2005)]

Voth, Gregory A.; Hone, Tyler D.

doi:10.1063/1.1839868

Cited by 8 publications

(7 citation statements)

References 17 publications

(5 reference statements)

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“…A  (i.e., Ĥ Ae     , the Boltzmann operator itself) is not invariant with the approximate evolution of the LSC-IVR for anharmonic systems 33, 64,92,126,127,[131][132][133][134] . The latter may lead to the unphysical decay (i.e., overdamping) intrinsic in the LSC-IVR correlation function, which becomes progressively worse for longer times 33, 135 .…”

Section: A Linearized Semiclassical Initial Value Representation Formentioning

confidence: 99%

Critical role of quantum dynamical effects in the Raman spectroscopy of liquid water

Liu

2018

Molecular Physics

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Understanding the Raman spectroscopy at the atomistic level is important for the elucidation of dynamical processes in liquid water. Because the polarizability (or its time derivative) is often a highly nonlinear function of coordinates or/and momenta, we employ the linearized semiclassical initial value representation for quantum dynamical simulations of liquid water (and heavy water) under ambient conditions based on an ab initio based, flexible, polarizable model (the POLI2VS force field). It is shown that quantum dynamical effects play a critical role in reproducing the peaks in the intermediate region between the librational and bending bands, those between the bending and stretching bands, and the double-peak in the stretching band in the experimental isotropic Raman spectrum. In contrast, quantum dynamical effects are important but less decisive in the anisotropic Raman spectrum. By selectively freezing either the intramolecular O-H stretching or H-O-H bending mode, we demonstrate that the peak in the intermediate region (2000-2400 cm -1 ) of the isotropic Raman spectrum arises from the interplay of the stretching and bending motions while a substantial part of the peak in the same intermediate region of the anisotropic Raman spectrum may be attributed to the combined motion of the bending and librational modes.

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Section: A Linearized Semiclassical Initial Value Representation Formentioning

confidence: 99%

Critical role of quantum dynamical effects in the Raman spectroscopy of liquid water

Liu

2018

Molecular Physics

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“…And perhaps most importantly Eq. 41 And the LSC-IVR approximation to the correlation function in Eq. 5,51,52 In particular, it can be obtained by linearizing the standard semiclassical initial value representation approximation to Eq.…”

Section: ͑32͒mentioning

confidence: 99%

Zero point energy leakage in condensed phase dynamics: An assessment of quantum simulation methods for liquid water

Habershon

Manolopoulos

2009

The Journal of Chemical Physics

141

172

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The approximate quantum mechanical ring polymer molecular dynamics (RPMD) and linearized semiclassical initial value representation (LSC-IVR) methods are compared and contrasted in a study of the dynamics of the flexible q-TIP4P/F water model at room temperature. For this water model, a RPMD simulation gives a diffusion coefficient that is only a few percent larger than the classical diffusion coefficient, whereas a LSC-IVR simulation gives a diffusion coefficient that is three times larger. We attribute this discrepancy to the unphysical leakage of initially quantized zero point energy (ZPE) from the intramolecular to the intermolecular modes of the liquid as the LSC-IVR simulation progresses. In spite of this problem, which is avoided by construction in RPMD, the LSC-IVR may still provide a useful approximation to certain short-time dynamical properties which are not so strongly affected by the ZPE leakage. We illustrate this with an application to the liquid water dipole absorption spectrum, for which the RPMD approximation breaks down at frequencies in the O-H stretching region owing to contamination from the internal modes of the ring polymer. The LSC-IVR does not suffer from this difficulty and it appears to provide quite a promising way to calculate condensed phase vibrational spectra.

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“…The ring-polymer and centroid molecular dynamics approximations both conserve the exact quantum mechanical equilibrium distribution, whereas the classical Wigner model involves purely classical trajectories that conserve the classical Boltzmann density e −␤H͕͑p j ͖,͕r j ͖͒ . As Voth and Hone have recently emphasized, 22 this difference can be quite significant when the quantum and classical equilibrium distributions differ in a fundamental way, as is now known to be the case for liquid parahydrogen at both of the present thermodynamic state points. 20 It is therefore not surprising that our Kubotransformed velocity autocorrelation functions disagree at long times with those of the classical Wigner model.…”

Section: A Velocity Autocorrelation Functionsmentioning

confidence: 99%

Quantum diffusion in liquid para-hydrogen from ring-polymer molecular dynamics

Miller

Manolopoulos²

2005

The Journal of Chemical Physics

155

140

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We have used the ring-polymer molecular dynamics method to calculate approximate Kubo-transformed velocity autocorrelation functions and self-diffusion coefficients for low-pressure liquid para-hydrogen at temperatures of 25 and 14 K. The resulting diffusion coefficients are shown to be consistent with experimental shear viscosities and the established finite-size relation D͑L͒ Ӎ D͑ϱ͒ − 2.837k B T /6L, where k B is the Boltzmann constant, T the absolute temperature, the shear viscosity, and L the length of the ͑cubic͒ simulation cell. The diffusion coefficients D͑L͒ obtained in simulations with finite system sizes are therefore too small. However, the extrapolation to infinite system size corrects this deficiency and leads to excellent agreement with experimental results. This both demonstrates the influence of system-size effects on quantum mechanical diffusion coefficients and provides further evidence that ring-polymer molecular dynamics is an accurate as well as practical way of including quantum effects in condensed phase molecular dynamics.

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Response to “Comment on ‘A centroid molecular dynamics study of liquid para-hydrogen and ortho-deuterium’ ” [J. Chem. Phys. 122, 057101 (2005)]

Cited by 8 publications

References 17 publications

Critical role of quantum dynamical effects in the Raman spectroscopy of liquid water

Critical role of quantum dynamical effects in the Raman spectroscopy of liquid water

Zero point energy leakage in condensed phase dynamics: An assessment of quantum simulation methods for liquid water

Quantum diffusion in liquid para-hydrogen from ring-polymer molecular dynamics

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