In search of the next Holy Grail of polyoxide chemistry: Explicitly correlated ab initio full quartic force fields for HOOH, HOOOH, HOOOOH, and their isotopologues

Abstract

Explicitly correlated ab initio methods have been used to compute full quartic force fields for the three chain minima for HOOOOH, which are found to lie within 1 kcal mol(-1). The CCSD(T)-F12 method with the cc-pVTZ-F12 basis set was used to compute equilibrium structures, anharmonic vibrational frequencies, and rotational constants for HOOH, HOOOH, and three chain isomers of HOOOOH, with the two former force fields being used as benchmarks for the latter three. The full quartic force fields were computed in such a way as to yield fundamental frequencies for all isotopologues at once. The present research confirms the recent experimental identification of HOOOH and provides reliable force fields in support of future experimental work on the enigmatic bonding paradigms involved in the HOOOOH chain.

An Evaluation of Gas Phase Enthalpies of Formation for Hydrogen-Oxygen (HxOy) Species

“…Earlier, Arnau and Giguere (1974) [208] measured three frequencies: ν 3 , ν 4 , and ν 8 . Hollman and Schaefer (2012) [200] computed anharmonic and harmonic frequencies (the latter are given in Table 12). Jackel (1993) [205] has also computed harmonic frequencies.…”

“…We have assigned an estimated (liberal) uncertainty of 1.2 kJ mol −1 considering the uncertainties in the quantum chemical calculations (see Table 9 for the range of computed values), zero point energies, and the contribution to the enthalpy from the torsions. We have corrected the Grant et al value slightly using the anharmonic ZPE computed by Hollman and Schaefer (2012) [200] and treating the torsions as hindered rotors (Grant et Table 10 is a summary of the selected values for the gas phase enthalpies of formation for each hydrogen-oxygen H x O y species as outlined in previous sections.…”

“…We have corrected their value slightly using the anharmonic ZPE computed by Hollman and Schaefer (2012) [200] and treated the torsions as hindered rotors (Grant et al treated them as vibrations). They used a ZPE of 6474 cm −1 (see Table 11) based on an average of the experimental fundamental frequencies (ν) and computed harmonic frequencies (ω e ).…”

On the role of excited species in hydrogen combustion

“…Hydrogen polyoxides, HOOOH, HOOOOH and radical HO 3 are not included as well. Although these species have recently received some attention as possible temporary reservoir of OH in atmosphere [46,47], they were never considered in combustion models, except in [48].…”

Arbitrary order El'yashevich–Wilson B tensor formulas for the most frequently used internal coordinates in molecular vibrational analyses

“…[1][2][3] The PES is central to our understanding of reactions, 4-8 structure, 9 dynamics, [10][11][12] and a plethora of spectroscopic properties. [13][14][15][16][17][18] Given the difficulties associated with probing even the simplest of PESs experimentally, [19][20][21] the theoretical evaluation of PESs for molecular systems has become one of the most critical and widely utilized roles of computation in modern chemistry and molecular physics. The construction of PESs requires a reasonable choice of coordinates to be made.…”