The effect of isotopic substitution and detailed balance on the infrared spectroscopy of water: A combined time correlation function and instantaneous normal mode analysis

Abstract

Isotope effects in liquid water by infrared spectroscopy. II. Factor analysis of the temperature effect on H 2 O and D 2 O A combined instantaneous normal mode and time correlation function description of the infrared vibrational spectrum of ambient waterWe have recently demonstrated that simple classical molecular dynamics methods are capable of nearly quantitatively reproducing most of the intermolecular and intramolecular infrared ͑IR͒ spectroscopy of water ͓H. Ahlborn, X. Ji, B. Space, and P. B. Moore, J. Chem. Phys. 111, 10622 ͑1999͔͒. Here it is demonstrated that the result is robust by quantitatively reproducing experimentally measured D 2 O IR spectroscopy utilizing the same models. This suggests that the quantum effects associated with light atom motion are relatively unimportant. Instantaneous normal mode ͑INM͒ theory and the time correlation function ͑TCF͒ methodology are used in a complimentary fashion to analyze the molecular origin of the IR spectroscopy of deuterated water (D 2 O). The TCF methods demonstrate that our models of the dynamics and the system dipole are reasonable by successful quantitative comparison of the theoretical spectrum with experimental results. INM methodology is then employed to analyze what condensed phase motions are responsible for the observed O-D stretching line shapes. It is surprising that classical models can reproduce the complex spectroscopy of both liquid H 2 O and D 2 O, and this result implies that the motions responsible for the signal must be effectively harmonic in nature. This assertion is supported by the drastic impact that is seen on both the intensity and line shape through the choice of detailed balance correction factor that is used to quantum correct the classical vibrational line shape.

Hydrogen bonds of interfacial water in human breast cancer tissue compared to lipid and DNA interfaces

“…The calculations of the vibrational band shapes of the OH stretching mode involved in H-bond interactions have a long history and have captured the attention of a number of papers [43][44][45][46][47][48][49][50][51][52][53][54][55][56][57][58][59][60][61]. In order to explain spectacular features in frequency shifts, band shapes, and bandwidths of the components the OH stretching modes the linear and nonlinear response theory [43][44][45], quantum ab inito calculations for possible cluster structures [62][63][64][65][66][67][68], classical [69][70][71][72][73] and mixed quantum/classical molecular dynamics simulations [74][75][76] have been used.…”

Can far-IR action spectroscopy combined with BOMD simulations be conformation selective?

“…For the prefactor in eqn (1), we have taken into account an empirical quantum correction factor (multiplying the classical line shape) of the form bho/(1 À exp (Àbho)), which was shown by us and others to give accurate results on calculated IR intensities. [43][44][45] For more detailed discussions on quantum corrections, see for instance ref. 46-49. The main advantages of the molecular dynamics (MD) approach in eqn (1) for the calculation of infrared spectra (also called ''dynamical spectra'' in the remainder of the text) are discussed in detail in our review 50 and are briefly listed as follows:…”

Environmental effects on vibrational proton dynamics in H5O2+: DFT study on crystalline H5O2+ClO4−

“…More sophisticated schemes 39,40 may lead to a more severe damping for low frequencies as found for liquid water. 41 The observed intensities also depend on the refractive index which in general is frequency dependent. 42 This dependence is unknown in most cases and has not been considered.…”