On the infrared and raman spectra of water in the region 5–250 cm−1

Static and dynamic dielectric properties of liquid ethanol have been studied as a function of the wave-vector number by computer simulation. Molecular dynamics simulations at room temperature have been performed using the optimized potentials for liquid simulations ͑OPLS͒ potential model proposed by Jorgensen ͓J. Phys. Chem. 90, 1276 ͑1986͔͒. The time dependent correlation functions of the longitudinal and transverse components of the dipole density as well as the individual and total dipole moment autocorrelation functions have been calculated. The infrared spectra and the dielectric relaxation of the liquid have been also analyzed. Results have been compared with the available experimental data. Special attention has been dedicated to investigate the molecular origin of the different analyzed properties.

Section: ␣͑ ͒ϭmentioning

confidence: 86%

Dielectric properties of liquid ethanol. A computer simulation study

Saiz

Guàrdia

Padró

2000

“…32 It is well established that simple point charge models of water, such as TIP4P/2005 34 or SPC/E, 35 cannot account for the intensity of that band, since that band originates from charge flows within and between water molecules upon hydrogen bonding. 5,[36][37][38][39] Adding polarizability to a water model, either in an ad hoc manner to a trajectory that has been precalculated with the help of a pointcharge model, [39][40][41][42] or explicitly as part of the force field, [43][44][45] reveals the band in the THz absorption spectrum, albeit, often, with severely underestimated intensity.…”

Section: Introductionmentioning

confidence: 99%

2D-Raman-THz spectroscopy: A sensitive test of polarizable water models

Hamm

2014

In a recent paper, the experimental 2D-Raman-THz response of liquid water at ambient conditions has been presented [J. Savolainen, S. Ahmed, and P. Hamm, Proc. Natl. Acad. Sci. U. S. A. 110, 20402 (2013)]. Here, all-atom molecular dynamics simulations are performed with the goal to reproduce the experimental results. To that end, the molecular response functions are calculated in a first step, and are then convoluted with the laser pulses in order to enable a direct comparison with the experimental results. The molecular dynamics simulation are performed with several different water models: TIP4P/2005, SWM4-NDP, and TL4P. As polarizability is essential to describe the 2D-Raman-THz response, the TIP4P/2005 water molecules are amended with either an isotropic or a anisotropic polarizability a posteriori after the molecular dynamics simulation. In contrast, SWM4-NDP and TL4P are intrinsically polarizable, and hence the 2D-Raman-THz response can be calculated in a self-consistent way, using the same force field as during the molecular dynamics simulation. It is found that the 2D-Raman-THz response depends extremely sensitively on details of the water model, and in particular on details of the description of polarizability. Despite the limited time resolution of the experiment, it could easily distinguish between various water models. Albeit not perfect, the overall best agreement with the experimental data is obtained for the TL4P water model. © 2014 AIP Publishing LLC. [http://dx

“…The far infrared 50 and depolarized Raman 51 spectra have a band near 200 cm Ϫ1 that is present in the calculated spectra only if polarization effects are included. 21,24,[52][53][54] This feature corresponds to translational vibration in the cage of a molecule's nearest neighbors. 55 This motion only shows up in the dielectric spectrum if it causes a change in the molecule's dipole moment magnitude, since it does not change its orientation.…”

Section: Introductionmentioning

confidence: 99%

Simulations of ice and liquid water over a range of temperatures using the fluctuating charge model

Rick

2001

178

159

Simulations of ice and liquid water over a range of temperatures using the fluctuating charge model The temperature dependence of the thermodynamic and dynamical properties of liquid water using the polarizable fluctuating charge ͑FQ͒ model is presented. The properties of ice Ih, both for a perfect lattice with no thermal disorder and at a temperature of 273 K, are also presented. In contrast to nonpolarizable models, the FQ model has a density maximum of water near 277 K. For ice, the model has a dipole moment of the perfect lattice of 3.05 Debye, in good agreement with a recent induction model calculation. The simulations at 273 K and the correct density find that thermal motion decreases the average dipole moment to 2.96 D. The liquid state dipole moment is less than the ice value and decreases with temperature.