Ab Initio Studies of Structural and Vibrational Properties of Protonated Water Cluster H₇O₃⁺ and Its Deuterium Isotopologues: An Application of Driven Molecular Dynamics

Abstract

In this work, we present infrared (IR) spectra of H7O3(+) and its deuterium isotopomers calculated by direct molecular dynamics (MD) simulations at the B3LYP/6-31+G** computational level. The calculated spectra obtained at 100, 300, and 500 K were compared to available experimental observations, and spectral features were assigned using normal-mode analysis (NMA) and driven molecular dynamics (DMD). Spectral peaks at 2410 and 2540 cm(-1) were assigned to asymmetric and symmetric stretches of the bridging hydrogen (BH) using NMA. The weak spectral features at 2166 and 2275 cm(-1) were assigned to a combination band of BH asymmetric stretch, H2O in phase wagging, OO stretch, and H3O(+) rocking vibrations by DMD simulations. Our observation of BH stretch vibrations as low as 2166 cm(-1) is in good agreement with the assignment of the low-resolution spectrum obtained by Schwarz at 2200-2300 cm(-1) [Schwarz, H. A. J. Chem. Phys. 1977, 67, 5525-5534] and vibrational predissociation spectrum by Lee et al. ∼2300 cm(-1) [Okumura, M.; Yeh, L. I.; Myers, J. D.; Lee, Y. T. J. Chem. Phys. 1990, 94, 3416-3427].

Ionization dynamics of the branched water cluster: A long-lived non-proton-transferred intermediate

“…Therefore, pure and protonated water clusters [1][2][3][4][5][6][7][8] and solute-water clusters [9][10][11][12][13][14][15][16][17][18][19][20][21][22] have been investigated both experimentally and theoretically. The photo-ionization of largesized water clusters has been studied using several experimental techniques [23][24][25][26].…”

A comprehensive search of topologically distinct local minimum structures of protonated water octamer and the classification of O H topological types

“…There can be many isomers and many local minima even for medium-sized PW clusters. Since structural properties of PW clusters are relevant to the understanding of thermodynamic properties and proton transfer mechanisms in aqueous solutions and biological systems, PW clusters have been extensively studied experimentally [1][2][3][4][5][6][7][8][9][10] as well as theoretically [11][12][13][14][15][16][17][18][19][20][21][22][23][24][25]. Since the number of possible structural isomers increases rapidly with the cluster size, it is difficult to present all of them even for medium-sized PW clusters.…”

Peculiarities of formation of hydroxonium ion and its small clusters

“…Geometry of hydroxonium ion clusters with several (up to 10) water molecules in gas and condensed phase has been studied in detail as well [20][21][22][23][24][25][26][27][28][29][30]. However, selectivity of the intermolecular bonding involving hydroxonium ion and its effect on the cluster nuclearity have remained the open issues so far.…”

“…Vibrational and electronic spectra were simulated using the B3LYP functional and the 6-311G** basis allowing the best coincidence between the experimental and the simulated О-Н dissociation energy and geometry parameters of Н 2 О molecule [18,[25][26][27][28]. On top of that, the B3LYP and B3PW91 functionals could adequately reproduce vibrational frequencies of the H 3 O + ion and its clusters with water molecules [15,16,23,[31][32][33][34][35]. Cross-sections of potential energy surfaces of formation and decomposition of Н 3 О + ion and Н 3 О neutral molecule…”

“…The optimized parameters of equilibrium states of the Zundel [25,30] and Eigen [21,30] hydroxonium ions, water molecule [18,[25][26][27][28], and the H 3 O + -n(Н 2 O) (n = 2, 3) complexes [18,23,29,30] obtained by us using the DFT method with different functionals (Tables 1 and 2) coincided with the results of spectral [16,42], resonance, and X-ray diffraction measurements as well as with the simulation data [16, 18-20, 25, 27-29, 33, 35, 36]. Cross-sections of potential energy surfaces of the…”