Calculation of the O−H Stretching Vibrational Overtone Spectrum of the Water Dimer (original) (raw)
Related papers
Journal of Physical Chemistry A, 2008
We have calculated frequencies and intensities of fundamental and overtone vibrational transitions in water and water dimer with use of different vibrational methods. We have compared results obtained with correlationcorrected vibrational self-consistent-field theory and vibrational second-order perturbation theory both using normal modes and finally with a harmonically coupled anharmonic oscillator local mode model including OH-stretching and HOH-bending local modes. The coupled cluster with singles, doubles, and perturbative triples ab initio method with augmented correlation-consistent triple-Dunning and atomic natural orbital basis sets has been used to obtain the necessary potential energy and dipole moment surfaces. We identify the strengths and weaknesses of these different vibrational approaches and compare our results to the available experimental results.
Australian Journal of Chemistry, 2014
The water dimer and its 11 deuterated isotopomers are investigated utilizing coupled cluster theory and experimental data as input for a perturbational determination of the isotopomer frequencies. Deuterium substitution reduces the H-bond stretching frequency by maximally 12 cm–1 from 143 to 131 cm–1, which makes a spectroscopic differentiation of H- and D-bonds difficult. However, utilizing the 132 frequencies obtained in this work, the identification of all isotopomers is straightforward. The CCSD(T)/CBS value of the binding energy De is 5.00 kcal mol–1. The binding energy D0 of the water dimer increases upon deuterium substitution from 3.28 to maximally 3.71 kcal mol–1 reflecting a decrease in the zero point energy contribution. The entropy values of the D-isotopomers increase from 73 to 77 entropy units in line with the general observation that a mass increase leads to larger entropies. All 12 isotopomers possess positive free binding energies at 80 K and a reduced pressure of 1...
2013
A recently computed, high-accuracy ab initio Born−Oppenheimer (BO) potential energy surface (PES) for the water molecule is combined with relativistic, adiabatic, quantum electrodynamics, and, crucially, nonadiabatic corrections. Calculations of ro-vibrational levels are presented for several water isotopologues and shown to have unprecedented accuracy. A purely ab initio calculation reproduces some 200 known band origins associated with seven isotopologues of water with a standard deviation (σ) of about 0.35 cm −1. Introducing three semiempirical scaling parameters, two affecting the BO PES and one controlling nonadiabatic effects, reduces σ below 0.1 cm −1. Introducing one further rotational nonadiabatic parameter gives σ better than 0.1 cm −1 for all observed rovibrational energy levels up to J = 25. We conjecture that the energy levels of closed-shell molecules with roughly the same number of electrons as water, such as NH 3 , CH 4 , and H 3 O + , could be calculated to this accuracy using an analogous procedure. This means that near-ab initio calculations are capable of predicting transition frequencies with an accuracy only about a factor of 5 worse than high resolution experiments.
Spectroscopic determination of the water dimer intermolecular potential-energy surface
The Journal of Chemical Physics, 2002
Two polarizable six-dimensional water dimer intermolecular potential surfaces have been determined by fitting the distributed multipole ASP ͑anisotropic site potential͒ potential form to microwave, terahertz, and midinfrared cavity ringdown (D 2 O) 2 spectra via a rigorous calculation of the water dimer eigenstates with the PSSH ͑pseudo-spectral split Hamiltonian͒ method. The fitted potentials accurately reproduce most ground-state vibration-rotation-tunneling spectra and yield excellent second virial coefficients for both H 2 O and D 2 O. The calculated dimer structure and dipole moment are close to those determined from microwave spectroscopy and high level ab initio calculations, except that the O-O distance ͑2.952 Å͒ is significantly shorter than the currently accepted experimental value. The dimer binding energy ͑4.85 kcal/mol͒ is considerably smaller than the accepted experimental result, but in excellent agreement with recent theoretical results, as are the acceptor switching and donor-acceptor interchange tunneling barriers and the cyclic water trimer and tetramer structures and binding energies.
Local vibrational modes of the water dimer – Comparison of theory and experiment
Chemical Physics Letters, 2012
Local and normal vibrational modes of the water dimer are calculated at the CCSD(T)/CBS level of theory. The local H-bond stretching frequency is 528 cm À1 compared to a normal mode stretching frequency of just 143 cm À1. The adiabatic connection scheme between local and normal vibrational modes reveals that the lowering is due to mass coupling, a change in the anharmonicity, and coupling with the local HOH bending modes. The local mode stretching force constant is related to the strength of the H-bond whereas the normal mode stretching force constant and frequency lead to an erroneous underestimation of the Hbond strength.
Spectroscopic Determination of the Water Pair Potential
Science, 1999
A polarizable water pair potential was determined by fitting a potential form to microwave, terahertz, and mid-infrared (D 2 O) 2 spectra through a rigorous calculation of the water dimer eigenstates. It accurately reproduces most ground state vibration-rotation-tunneling spectra and yields excellent second viral coefficients. The calculated dimer structure and dipole moment are very close to those determined from microwave spectroscopy and high-level ab initio calculations. The dimer binding energy and acceptor switching and donor-acceptor interchange tunneling barriers are in excellent agreement with recent ab initio theory, as are cyclic water trimer and tetramer structures and binding energies.
Angewandte Chemie International Edition, 2019
Using the helium nanodroplet isolation setup at the ultrabright free-electron laser source FELIX in Nijmegen (BoHeNDI@FELIX), the intermolecular modes of water dimer in the frequency region from 70 to 550 cm À1 were recorded. Observed bands were assigned to donor torsion, acceptor wag, acceptor twist, intermolecular stretch, donor torsion overtone, and in-plane and out-of-plane librational modes. This experimental data set provides a sensitive test for state-of-the-art water potentials and dipole moment surfaces. Theoretical calculations of the IR spectrum are presented using high-level quantum and approximate quasiclassical molecular dynamics approaches. These calculations use the full-dimensional ab initio WHHB potential and dipole moment surfaces. Based on the experimental data, a considerable increase of the acceptor switch and a bifurcation tunneling splitting in the librational mode is deduced, which is a consequence of the effective decrease in the tunneling barrier.
Chemical Physics, 1983
The dipole-moment derivatives and infrared-absorption intensities of the water dimer including scveml det~terxed 3pscis.s have been calculated using sb initio SCF techniques. The resuhs xs compsrrd \\ith ths :malogous qtuntirirrs for monomeric w;lter. In addition to the highly enhanced intensity of the immmolsculnr OH zmxch mew inrem~olaxdar modes that oc'cur in the 90400 cm-' region are also found to be very intense. An electrostatic model for the w:tter dimsr ha been explored with I view to devrtoping a possible scheme for the cltlculntion of infrared intensities of Ixger clusters. AS ;L rsa~lt of the significrtnt exchange and charge-transfer effects such a model is found to hs unrsliablr in dacrihing thi: drpok-mamat derivatives that directly involve the hydrogen bond.
Journal of Quantitative Spectroscopy and Radiative Transfer, 2010
A new, accurate, global, mass-independent, first-principles potential energy surface (PES) is presented for the ground electronic state of the water molecule. The PES is based on 2200 energy points computed at the all-electron aug-cc-pCV6Z IC-MRCI(8,2) level of electronic structure theory and includes the relativistic one-electron massvelocity and Darwin corrections. For H 2 16 O, the PES has a dissociation energy of D 0 = 41 109 cm À 1 and supports 1150 vibrational energy levels up to 41 083 cm À 1 . The deviation between the computed and the experimentally measured energy levels is below 15 cm À 1 for all the states with energies less than 39 000 cm À 1 . Characterization of approximate vibrational quantum numbers is performed using several techniques: energy decomposition, wave function plots, normal mode distribution, expectation values of the squares of internal coordinates, and perturbing the bending part of the PES. Vibrational normal mode labels, though often not physically meaningful, have been assigned to all the states below 26 500 cm À 1 and to many more above it, including some highly excited stretching states all the way to dissociation. Issues to do with calculating vibrational band intensities for the higher-lying states are discussed.
Infrared Spectrum of the Protonated Water Dimer
2007
Accurate infrared spectroscopy of protonated water clusters that are prepared in the gas phase has become possible in recent years, thus opening the door to a deeper understanding of the properties of aqueous systems and the hydrated proton, which are of high interest in central areas of chemistry and biology. Several computational studies have appeared in parallel, providing a necessary theoretical basis for the assignment and understanding of the different spectral features. It has been recently demonstrated that the H 5 O 2 + motif, also referred to as the Zundel cation, plays an important role in protonated water clusters of six or more water molecules and, together with the Eigen cation (H 9 O 4 + ), as a limiting structure of the hydrated proton in bulk water. 11] The importance of the hydrated proton and the amount of work devoted to the problem contrast with the fact that the smallest system in which a proton is shared between water molecules, H 5 O 2 + , is not yet completely understood, and an explanation of the most important spectral signatures and the associated dynamics of the cluster is lacking.