Vibrational Frequency

14,000,000 Leading Edge Experts on the ideXlab platform

Scan Science and Technology

Contact Leading Edge Experts & Companies

Scan Science and Technology

Contact Leading Edge Experts & Companies

The Experts below are selected from a list of 97290 Experts worldwide ranked by ideXlab platform

Bartosz Blasiak - One of the best experts on this subject based on the ideXlab platform.

  • Vibrational solvatochromism of nitrile infrared probes beyond the Vibrational stark dipole approach
    Physical Chemistry Chemical Physics, 2016
    Co-Authors: Bartosz Blasiak, Andrew W Ritchie, Lauren J Webb
    Abstract:

    Systematic probing of local environments around biopolymers is important for understanding their functions. Therefore, there has been growing interest in in situ measurements of molecular granularity and heterogeneity through the systematic analysis of Vibrational Frequency shifts of carbonyl and nitrile infrared probes by Vibrational Stark dipole theory. However, here we show that the nitrile Vibrational Frequency shift induced by its interaction with the surrounding molecules cannot be solely described by electric field-based theory because of the exchange–repulsion and dispersion interaction contributions. Considering a variety of molecular environments ranging from bulk solutions to protein environments, we explore the distinct scenarios of solute-environment contacts and their traces in Vibrational Frequency shifts. We believe that the present work could provide a set of clues that could be potentially used to design a rigorous theoretical model linking Vibrational solvatochromism and molecular topology in complex heterogeneous environments.

  • Vibrational solvatochromism ii a first principle theory of solvation induced Vibrational Frequency shift based on effective fragment potential method
    Journal of Chemical Physics, 2014
    Co-Authors: Bartosz Blasiak
    Abstract:

    Vibrational solvatochromism is a solvation-induced effect on fundamental Vibrational frequencies of molecules in solutions. Here we present a detailed first-principle coarse-grained theory of Vibrational solvatochromism, which is an extension of our previous work [B. Blasiak, H. Lee, and M. Cho, J. Chem. Phys. 139(4), 044111 (2013)] by taking into account electrostatic, exchange-repulsion, polarization, and charge-transfer interactions. By applying our theory to the model N-methylacetamide-water clusters, solute-solvent interaction-induced effects on amide I Vibrational Frequency are fully elucidated at Hartree-Fock level. Although the electrostatic interaction between distributed multipole moments of solute and solvent molecules plays the dominant role, the contributions from exchange repulsion and induced dipole-electric field interactions are found to be of comparable importance in short distance range, whereas the charge-transfer effect is negligible. The overall Frequency shifts calculated by taking ...

  • Vibrational solvatochromism towards systematic approach to modeling solvation phenomena
    Journal of Chemical Physics, 2013
    Co-Authors: Bartosz Blasiak
    Abstract:

    Vibrational solvatochromic Frequency shift of IR probe is an effect of interaction between local electric field and IR probe in condensed phases. Despite prolonged efforts to develop empirical maps for Vibrational Frequency shifts and transition dipoles of IR probes, a systematic approach to ab initio calculation of Vibrational solvatochromic charges and multipoles has not been developed. Here, we report on density functional theory (DFT) calculations of N-methylacetamide (NMA) Frequency shifts using implicit and coarse-grained models. The solvatochromic infrared spectral shifts are estimated based on the distributed multipole analysis of electronic densities calculated for gas-phase equilibrium structure of NMA. Thus obtained distributed solvatochromic multipole parameters are used to calculate the amide I Vibrational Frequency shifts of NMA in water clusters that mimic the instantaneous configurations of the liquid water. Our results indicate that the spectral shifts are primarily electrostatic in natur...

Zlatko Bacic - One of the best experts on this subject based on the ideXlab platform.

  • h2 hd and d2 in the small cage of structure ii clathrate hydrate Vibrational Frequency shifts from fully coupled quantum six dimensional calculations of the vibration translation rotation eigenstates
    Journal of Chemical Physics, 2019
    Co-Authors: David Lauvergnat, Yohann Scribano, David M Benoit, Zlatko Bacic, Peter Felker
    Abstract:

    We report the first fully coupled quantum six-dimensional (6D) bound-state calculations of the vibration-translation-rotation eigenstates of a flexible H2, HD, and D2 molecule confined inside the small cage of the structure II clathrate hydrate embedded in larger hydrate domains with up to 76 H2O molecules, treated as rigid. Our calculations use a pairwise-additive 6D intermolecular potential energy surface for H2 in the hydrate domain, based on an ab initio 6D H2–H2O pair potential for flexible H2 and rigid H2O. They extend to the first excited (v = 1) Vibrational state of H2, along with two isotopologues, providing a direct computation of Vibrational Frequency shifts. We show that obtaining a converged v = 1 Vibrational state of the caged molecule does not require converging the very large number of intermolecular translation-rotation states belonging to the v = 0 manifold up to the energy of the intramolecular stretch fundamental (≈4100 cm−1 for H2). Only a relatively modest-size basis for the intermolecular degrees of freedom is needed to accurately describe the Vibrational averaging over the delocalized wave function of the quantum ground state of the system. For the caged H2, our computed fundamental translational excitations, rotational j = 0 → 1 transitions, and Frequency shifts of the stretch fundamental are in excellent agreement with recent quantum 5D (rigid H2) results [A. Powers et al., J. Chem. Phys. 148, 144304 (2018)]. Our computed Frequency shift of −43 cm−1 for H2 is only 14% away from the experimental value at 20 K.We report the first fully coupled quantum six-dimensional (6D) bound-state calculations of the vibration-translation-rotation eigenstates of a flexible H2, HD, and D2 molecule confined inside the small cage of the structure II clathrate hydrate embedded in larger hydrate domains with up to 76 H2O molecules, treated as rigid. Our calculations use a pairwise-additive 6D intermolecular potential energy surface for H2 in the hydrate domain, based on an ab initio 6D H2–H2O pair potential for flexible H2 and rigid H2O. They extend to the first excited (v = 1) Vibrational state of H2, along with two isotopologues, providing a direct computation of Vibrational Frequency shifts. We show that obtaining a converged v = 1 Vibrational state of the caged molecule does not require converging the very large number of intermolecular translation-rotation states belonging to the v = 0 manifold up to the energy of the intramolecular stretch fundamental (≈4100 cm−1 for H2). Only a relatively modest-size basis for the intermol...

  • the effect of the condensed phase environment on the Vibrational Frequency shift of a hydrogen molecule inside clathrate hydrates
    Journal of Chemical Physics, 2018
    Co-Authors: Anna Powers, Yohann Scribano, David Lauvergnat, Else Mebe, David M Benoit, Zlatko Bacic
    Abstract:

    We report a theoretical study of the Frequency shift (redshift) of the stretching fundamental transition of an H2 molecule confined inside the small dodecahedral cage of the structure II clathrate hydrate and its dependence on the condensed-phase environment. In order to determine how much the hydrate water molecules beyond the confining small cage contribute to the Vibrational Frequency shift, quantum five-dimensional (5D) calculations of the coupled translation-rotation eigenstates are performed for H2 in the v=0 and v=1 Vibrational states inside spherical clathrate hydrate domains of increasing radius and a growing number of water molecules, ranging from 20 for the isolated small cage to over 1900. In these calculations, both H2 and the water domains are treated as rigid. The 5D intermolecular potential energy surface (PES) of H2 inside a hydrate domain is assumed to be pairwise additive. The H2–H2O pair interaction, represented by the 5D (rigid monomer) PES that depends on the Vibrational state of H2, v=0 or v=1, is derived from the high-quality ab initio full-dimensional (9D) PES of the H2–H2O complex [P. Valiron et al., J. Chem. Phys. 129, 134306 (2008)]. The H2 Vibrational Frequency shift calculated for the largest clathrate domain considered, which mimics the condensed-phase environment, is about 10% larger in magnitude than that obtained by taking into account only the small cage. The calculated splittings of the translational fundamental of H2 change very little with the domain size, unlike the H2 j = 1 rotational splittings that decrease significantly as the domain size increases. The changes in both the Vibrational Frequency shift and the j = 1 rotational splitting due to the condensed-phase effects arise predominantly from the H2O molecules in the first three complete hydration shells around H2.We report a theoretical study of the Frequency shift (redshift) of the stretching fundamental transition of an H2 molecule confined inside the small dodecahedral cage of the structure II clathrate hydrate and its dependence on the condensed-phase environment. In order to determine how much the hydrate water molecules beyond the confining small cage contribute to the Vibrational Frequency shift, quantum five-dimensional (5D) calculations of the coupled translation-rotation eigenstates are performed for H2 in the v=0 and v=1 Vibrational states inside spherical clathrate hydrate domains of increasing radius and a growing number of water molecules, ranging from 20 for the isolated small cage to over 1900. In these calculations, both H2 and the water domains are treated as rigid. The 5D intermolecular potential energy surface (PES) of H2 inside a hydrate domain is assumed to be pairwise additive. The H2–H2O pair interaction, represented by the 5D (rigid monomer) PES that depends on the Vibrational state of H2,...

David Lauvergnat - One of the best experts on this subject based on the ideXlab platform.

  • h2 hd and d2 in the small cage of structure ii clathrate hydrate Vibrational Frequency shifts from fully coupled quantum six dimensional calculations of the vibration translation rotation eigenstates
    Journal of Chemical Physics, 2019
    Co-Authors: David Lauvergnat, Yohann Scribano, David M Benoit, Zlatko Bacic, Peter Felker
    Abstract:

    We report the first fully coupled quantum six-dimensional (6D) bound-state calculations of the vibration-translation-rotation eigenstates of a flexible H2, HD, and D2 molecule confined inside the small cage of the structure II clathrate hydrate embedded in larger hydrate domains with up to 76 H2O molecules, treated as rigid. Our calculations use a pairwise-additive 6D intermolecular potential energy surface for H2 in the hydrate domain, based on an ab initio 6D H2–H2O pair potential for flexible H2 and rigid H2O. They extend to the first excited (v = 1) Vibrational state of H2, along with two isotopologues, providing a direct computation of Vibrational Frequency shifts. We show that obtaining a converged v = 1 Vibrational state of the caged molecule does not require converging the very large number of intermolecular translation-rotation states belonging to the v = 0 manifold up to the energy of the intramolecular stretch fundamental (≈4100 cm−1 for H2). Only a relatively modest-size basis for the intermolecular degrees of freedom is needed to accurately describe the Vibrational averaging over the delocalized wave function of the quantum ground state of the system. For the caged H2, our computed fundamental translational excitations, rotational j = 0 → 1 transitions, and Frequency shifts of the stretch fundamental are in excellent agreement with recent quantum 5D (rigid H2) results [A. Powers et al., J. Chem. Phys. 148, 144304 (2018)]. Our computed Frequency shift of −43 cm−1 for H2 is only 14% away from the experimental value at 20 K.We report the first fully coupled quantum six-dimensional (6D) bound-state calculations of the vibration-translation-rotation eigenstates of a flexible H2, HD, and D2 molecule confined inside the small cage of the structure II clathrate hydrate embedded in larger hydrate domains with up to 76 H2O molecules, treated as rigid. Our calculations use a pairwise-additive 6D intermolecular potential energy surface for H2 in the hydrate domain, based on an ab initio 6D H2–H2O pair potential for flexible H2 and rigid H2O. They extend to the first excited (v = 1) Vibrational state of H2, along with two isotopologues, providing a direct computation of Vibrational Frequency shifts. We show that obtaining a converged v = 1 Vibrational state of the caged molecule does not require converging the very large number of intermolecular translation-rotation states belonging to the v = 0 manifold up to the energy of the intramolecular stretch fundamental (≈4100 cm−1 for H2). Only a relatively modest-size basis for the intermol...

  • H$_2$, HD and D$_2$ in the small cage of structure II clathrate hydrate: Vibrational Frequency shifts from fully coupled quantum six-dimensional calculations of the vibration-translation-rotation eigenstates
    Journal of Chemical Physics, 2019
    Co-Authors: David Lauvergnat, Yohann Scribano, David Benoit, Peter Felker, Zlatko Bačić
    Abstract:

    We report the first fully coupled quantum 6D bound-state calculations of the vibration-translation-rotation (VTR) eigenstates of a fexible H$_2$, HD, and D$_2$ molecule confined in the small cage of the sII clathrate hydrate embedded in larger hydrate domains, treated as rigid. These calculations extend to the first excited (v = 1) Vibrational state of H$_2$ and the two isotopologues, and allow direct computation of its Vibrational Frequency shift. For the caged H$_2$, the fundamental translational excitations, the rotational $j = 0 \rightarrow 1$ transitions, and the Frequency shifts of the stretch fundamental from these quantum 6D calculations are in excellent agreement with the corresponding results of the recent quantum 5D (rigid H$_2$) treatment [A. Powers et al., J. Chem. Phys. 148, 144304 (2018)].

  • The effect of the condensed-phase environment on the Vibrational Frequency shift of a hydrogen molecule inside clathrate hydrates
    Journal of Chemical Physics, 2018
    Co-Authors: Anna Powers, Yohann Scribano, David Lauvergnat, Else Mebe, David Benoit, Zlatko Bačić
    Abstract:

    We report a theoretical study of the Frequency shift (redshift) of the stretching fundamental transition of an H2 molecule confined inside the small dodecahedral cage of the structure II clathrate hydrate and its dependence on the condensed-phase environment. In order to determine how much the hydrate water molecules beyond the confining small cage contribute to the Vibrational Frequency shift, quantum five-dimensional (5D) calculations of the coupled translation-rotation eigenstates are performed for H2 in the v=0 and v=1 Vibrational states inside spherical clathrate hydrate domains of increasing radius and a growing number of water molecules, ranging from 20 for the isolated small cage to over 1900. In these calculations, both H2 and the water domains are treated as rigid. The 5D intermolecular potential energy surface (PES) of H2 inside a hydrate domain is assumed to be pairwise additive. The H2–H2O pair interaction, represented by the 5D (rigid monomer) PES that depends on the Vibrational state of H2, v=0 or v=1, is derived from the high-quality ab initio full-dimensional (9D) PES of the H2–H2O complex [P. Valiron et al., J. Chem. Phys. 129, 134306 (2008)]. The H2 Vibrational Frequency shift calculated for the largest clathrate domain considered, which mimics the condensed-phase environment, is about 10% larger in magnitude than that obtained by taking into account only the small cage. The calculated splittings of the translational fundamental of H2 change very little with the domain size, unlike the H2 j = 1 rotational splittings that decrease significantly as the domain size increases. The changes in both the Vibrational Frequency shift and the j = 1 rotational splitting due to the condensed-phase effects arise predominantly from the H2O molecules in the first three complete hydration shells around H2.

  • the effect of the condensed phase environment on the Vibrational Frequency shift of a hydrogen molecule inside clathrate hydrates
    Journal of Chemical Physics, 2018
    Co-Authors: Anna Powers, Yohann Scribano, David Lauvergnat, Else Mebe, David M Benoit, Zlatko Bacic
    Abstract:

    We report a theoretical study of the Frequency shift (redshift) of the stretching fundamental transition of an H2 molecule confined inside the small dodecahedral cage of the structure II clathrate hydrate and its dependence on the condensed-phase environment. In order to determine how much the hydrate water molecules beyond the confining small cage contribute to the Vibrational Frequency shift, quantum five-dimensional (5D) calculations of the coupled translation-rotation eigenstates are performed for H2 in the v=0 and v=1 Vibrational states inside spherical clathrate hydrate domains of increasing radius and a growing number of water molecules, ranging from 20 for the isolated small cage to over 1900. In these calculations, both H2 and the water domains are treated as rigid. The 5D intermolecular potential energy surface (PES) of H2 inside a hydrate domain is assumed to be pairwise additive. The H2–H2O pair interaction, represented by the 5D (rigid monomer) PES that depends on the Vibrational state of H2, v=0 or v=1, is derived from the high-quality ab initio full-dimensional (9D) PES of the H2–H2O complex [P. Valiron et al., J. Chem. Phys. 129, 134306 (2008)]. The H2 Vibrational Frequency shift calculated for the largest clathrate domain considered, which mimics the condensed-phase environment, is about 10% larger in magnitude than that obtained by taking into account only the small cage. The calculated splittings of the translational fundamental of H2 change very little with the domain size, unlike the H2 j = 1 rotational splittings that decrease significantly as the domain size increases. The changes in both the Vibrational Frequency shift and the j = 1 rotational splitting due to the condensed-phase effects arise predominantly from the H2O molecules in the first three complete hydration shells around H2.We report a theoretical study of the Frequency shift (redshift) of the stretching fundamental transition of an H2 molecule confined inside the small dodecahedral cage of the structure II clathrate hydrate and its dependence on the condensed-phase environment. In order to determine how much the hydrate water molecules beyond the confining small cage contribute to the Vibrational Frequency shift, quantum five-dimensional (5D) calculations of the coupled translation-rotation eigenstates are performed for H2 in the v=0 and v=1 Vibrational states inside spherical clathrate hydrate domains of increasing radius and a growing number of water molecules, ranging from 20 for the isolated small cage to over 1900. In these calculations, both H2 and the water domains are treated as rigid. The 5D intermolecular potential energy surface (PES) of H2 inside a hydrate domain is assumed to be pairwise additive. The H2–H2O pair interaction, represented by the 5D (rigid monomer) PES that depends on the Vibrational state of H2,...

Zlatko Bačić - One of the best experts on this subject based on the ideXlab platform.

  • H$_2$, HD and D$_2$ in the small cage of structure II clathrate hydrate: Vibrational Frequency shifts from fully coupled quantum six-dimensional calculations of the vibration-translation-rotation eigenstates
    Journal of Chemical Physics, 2019
    Co-Authors: David Lauvergnat, Yohann Scribano, David Benoit, Peter Felker, Zlatko Bačić
    Abstract:

    We report the first fully coupled quantum 6D bound-state calculations of the vibration-translation-rotation (VTR) eigenstates of a fexible H$_2$, HD, and D$_2$ molecule confined in the small cage of the sII clathrate hydrate embedded in larger hydrate domains, treated as rigid. These calculations extend to the first excited (v = 1) Vibrational state of H$_2$ and the two isotopologues, and allow direct computation of its Vibrational Frequency shift. For the caged H$_2$, the fundamental translational excitations, the rotational $j = 0 \rightarrow 1$ transitions, and the Frequency shifts of the stretch fundamental from these quantum 6D calculations are in excellent agreement with the corresponding results of the recent quantum 5D (rigid H$_2$) treatment [A. Powers et al., J. Chem. Phys. 148, 144304 (2018)].

  • The effect of the condensed-phase environment on the Vibrational Frequency shift of a hydrogen molecule inside clathrate hydrates
    Journal of Chemical Physics, 2018
    Co-Authors: Anna Powers, Yohann Scribano, David Lauvergnat, Else Mebe, David Benoit, Zlatko Bačić
    Abstract:

    We report a theoretical study of the Frequency shift (redshift) of the stretching fundamental transition of an H2 molecule confined inside the small dodecahedral cage of the structure II clathrate hydrate and its dependence on the condensed-phase environment. In order to determine how much the hydrate water molecules beyond the confining small cage contribute to the Vibrational Frequency shift, quantum five-dimensional (5D) calculations of the coupled translation-rotation eigenstates are performed for H2 in the v=0 and v=1 Vibrational states inside spherical clathrate hydrate domains of increasing radius and a growing number of water molecules, ranging from 20 for the isolated small cage to over 1900. In these calculations, both H2 and the water domains are treated as rigid. The 5D intermolecular potential energy surface (PES) of H2 inside a hydrate domain is assumed to be pairwise additive. The H2–H2O pair interaction, represented by the 5D (rigid monomer) PES that depends on the Vibrational state of H2, v=0 or v=1, is derived from the high-quality ab initio full-dimensional (9D) PES of the H2–H2O complex [P. Valiron et al., J. Chem. Phys. 129, 134306 (2008)]. The H2 Vibrational Frequency shift calculated for the largest clathrate domain considered, which mimics the condensed-phase environment, is about 10% larger in magnitude than that obtained by taking into account only the small cage. The calculated splittings of the translational fundamental of H2 change very little with the domain size, unlike the H2 j = 1 rotational splittings that decrease significantly as the domain size increases. The changes in both the Vibrational Frequency shift and the j = 1 rotational splitting due to the condensed-phase effects arise predominantly from the H2O molecules in the first three complete hydration shells around H2.

Yohann Scribano - One of the best experts on this subject based on the ideXlab platform.

  • h2 hd and d2 in the small cage of structure ii clathrate hydrate Vibrational Frequency shifts from fully coupled quantum six dimensional calculations of the vibration translation rotation eigenstates
    Journal of Chemical Physics, 2019
    Co-Authors: David Lauvergnat, Yohann Scribano, David M Benoit, Zlatko Bacic, Peter Felker
    Abstract:

    We report the first fully coupled quantum six-dimensional (6D) bound-state calculations of the vibration-translation-rotation eigenstates of a flexible H2, HD, and D2 molecule confined inside the small cage of the structure II clathrate hydrate embedded in larger hydrate domains with up to 76 H2O molecules, treated as rigid. Our calculations use a pairwise-additive 6D intermolecular potential energy surface for H2 in the hydrate domain, based on an ab initio 6D H2–H2O pair potential for flexible H2 and rigid H2O. They extend to the first excited (v = 1) Vibrational state of H2, along with two isotopologues, providing a direct computation of Vibrational Frequency shifts. We show that obtaining a converged v = 1 Vibrational state of the caged molecule does not require converging the very large number of intermolecular translation-rotation states belonging to the v = 0 manifold up to the energy of the intramolecular stretch fundamental (≈4100 cm−1 for H2). Only a relatively modest-size basis for the intermolecular degrees of freedom is needed to accurately describe the Vibrational averaging over the delocalized wave function of the quantum ground state of the system. For the caged H2, our computed fundamental translational excitations, rotational j = 0 → 1 transitions, and Frequency shifts of the stretch fundamental are in excellent agreement with recent quantum 5D (rigid H2) results [A. Powers et al., J. Chem. Phys. 148, 144304 (2018)]. Our computed Frequency shift of −43 cm−1 for H2 is only 14% away from the experimental value at 20 K.We report the first fully coupled quantum six-dimensional (6D) bound-state calculations of the vibration-translation-rotation eigenstates of a flexible H2, HD, and D2 molecule confined inside the small cage of the structure II clathrate hydrate embedded in larger hydrate domains with up to 76 H2O molecules, treated as rigid. Our calculations use a pairwise-additive 6D intermolecular potential energy surface for H2 in the hydrate domain, based on an ab initio 6D H2–H2O pair potential for flexible H2 and rigid H2O. They extend to the first excited (v = 1) Vibrational state of H2, along with two isotopologues, providing a direct computation of Vibrational Frequency shifts. We show that obtaining a converged v = 1 Vibrational state of the caged molecule does not require converging the very large number of intermolecular translation-rotation states belonging to the v = 0 manifold up to the energy of the intramolecular stretch fundamental (≈4100 cm−1 for H2). Only a relatively modest-size basis for the intermol...

  • H$_2$, HD and D$_2$ in the small cage of structure II clathrate hydrate: Vibrational Frequency shifts from fully coupled quantum six-dimensional calculations of the vibration-translation-rotation eigenstates
    Journal of Chemical Physics, 2019
    Co-Authors: David Lauvergnat, Yohann Scribano, David Benoit, Peter Felker, Zlatko Bačić
    Abstract:

    We report the first fully coupled quantum 6D bound-state calculations of the vibration-translation-rotation (VTR) eigenstates of a fexible H$_2$, HD, and D$_2$ molecule confined in the small cage of the sII clathrate hydrate embedded in larger hydrate domains, treated as rigid. These calculations extend to the first excited (v = 1) Vibrational state of H$_2$ and the two isotopologues, and allow direct computation of its Vibrational Frequency shift. For the caged H$_2$, the fundamental translational excitations, the rotational $j = 0 \rightarrow 1$ transitions, and the Frequency shifts of the stretch fundamental from these quantum 6D calculations are in excellent agreement with the corresponding results of the recent quantum 5D (rigid H$_2$) treatment [A. Powers et al., J. Chem. Phys. 148, 144304 (2018)].

  • The effect of the condensed-phase environment on the Vibrational Frequency shift of a hydrogen molecule inside clathrate hydrates
    Journal of Chemical Physics, 2018
    Co-Authors: Anna Powers, Yohann Scribano, David Lauvergnat, Else Mebe, David Benoit, Zlatko Bačić
    Abstract:

    We report a theoretical study of the Frequency shift (redshift) of the stretching fundamental transition of an H2 molecule confined inside the small dodecahedral cage of the structure II clathrate hydrate and its dependence on the condensed-phase environment. In order to determine how much the hydrate water molecules beyond the confining small cage contribute to the Vibrational Frequency shift, quantum five-dimensional (5D) calculations of the coupled translation-rotation eigenstates are performed for H2 in the v=0 and v=1 Vibrational states inside spherical clathrate hydrate domains of increasing radius and a growing number of water molecules, ranging from 20 for the isolated small cage to over 1900. In these calculations, both H2 and the water domains are treated as rigid. The 5D intermolecular potential energy surface (PES) of H2 inside a hydrate domain is assumed to be pairwise additive. The H2–H2O pair interaction, represented by the 5D (rigid monomer) PES that depends on the Vibrational state of H2, v=0 or v=1, is derived from the high-quality ab initio full-dimensional (9D) PES of the H2–H2O complex [P. Valiron et al., J. Chem. Phys. 129, 134306 (2008)]. The H2 Vibrational Frequency shift calculated for the largest clathrate domain considered, which mimics the condensed-phase environment, is about 10% larger in magnitude than that obtained by taking into account only the small cage. The calculated splittings of the translational fundamental of H2 change very little with the domain size, unlike the H2 j = 1 rotational splittings that decrease significantly as the domain size increases. The changes in both the Vibrational Frequency shift and the j = 1 rotational splitting due to the condensed-phase effects arise predominantly from the H2O molecules in the first three complete hydration shells around H2.

  • the effect of the condensed phase environment on the Vibrational Frequency shift of a hydrogen molecule inside clathrate hydrates
    Journal of Chemical Physics, 2018
    Co-Authors: Anna Powers, Yohann Scribano, David Lauvergnat, Else Mebe, David M Benoit, Zlatko Bacic
    Abstract:

    We report a theoretical study of the Frequency shift (redshift) of the stretching fundamental transition of an H2 molecule confined inside the small dodecahedral cage of the structure II clathrate hydrate and its dependence on the condensed-phase environment. In order to determine how much the hydrate water molecules beyond the confining small cage contribute to the Vibrational Frequency shift, quantum five-dimensional (5D) calculations of the coupled translation-rotation eigenstates are performed for H2 in the v=0 and v=1 Vibrational states inside spherical clathrate hydrate domains of increasing radius and a growing number of water molecules, ranging from 20 for the isolated small cage to over 1900. In these calculations, both H2 and the water domains are treated as rigid. The 5D intermolecular potential energy surface (PES) of H2 inside a hydrate domain is assumed to be pairwise additive. The H2–H2O pair interaction, represented by the 5D (rigid monomer) PES that depends on the Vibrational state of H2, v=0 or v=1, is derived from the high-quality ab initio full-dimensional (9D) PES of the H2–H2O complex [P. Valiron et al., J. Chem. Phys. 129, 134306 (2008)]. The H2 Vibrational Frequency shift calculated for the largest clathrate domain considered, which mimics the condensed-phase environment, is about 10% larger in magnitude than that obtained by taking into account only the small cage. The calculated splittings of the translational fundamental of H2 change very little with the domain size, unlike the H2 j = 1 rotational splittings that decrease significantly as the domain size increases. The changes in both the Vibrational Frequency shift and the j = 1 rotational splitting due to the condensed-phase effects arise predominantly from the H2O molecules in the first three complete hydration shells around H2.We report a theoretical study of the Frequency shift (redshift) of the stretching fundamental transition of an H2 molecule confined inside the small dodecahedral cage of the structure II clathrate hydrate and its dependence on the condensed-phase environment. In order to determine how much the hydrate water molecules beyond the confining small cage contribute to the Vibrational Frequency shift, quantum five-dimensional (5D) calculations of the coupled translation-rotation eigenstates are performed for H2 in the v=0 and v=1 Vibrational states inside spherical clathrate hydrate domains of increasing radius and a growing number of water molecules, ranging from 20 for the isolated small cage to over 1900. In these calculations, both H2 and the water domains are treated as rigid. The 5D intermolecular potential energy surface (PES) of H2 inside a hydrate domain is assumed to be pairwise additive. The H2–H2O pair interaction, represented by the 5D (rigid monomer) PES that depends on the Vibrational state of H2,...