Energies of CH2OH, CH3O, and related compounds

The exact and phaseless variants of Auxiliary-Field Quantum Monte Carlo (AFQMC) have been shown to be capable of producing accurate ground-state energies for a wide variety of systems including those which exhibit substantial electron correlation effects. The computational cost of performing these calculations has to date been relatively high, impeding many important applications of these approaches. Here we present a correlated sampling methodology for AFQMC which relies on error cancellation to dramatically accelerate the calculation of energy differences of relevance to chemical transformations. In particular, we show that our correlated sampling-based AFQMC approach is capable of calculating redox properties, deprotonation free-energies, and hydrogen abstraction energies in an efficient manner without sacrificing accuracy. We validate the computational protocol by calculating the ionization potentials and electron affinities of the atoms contained in the G2 Test Set, and then proceed to utilize a composite method, which treats fixedgeometry processes with correlated sampling-based AFQMC and relaxation energies via MP2, to compute the ionization potential, deprotonation free-energy, and the O-H bond disocciation energy of methanol, all to within chemical accuracy. We show that the efficiency of correlated sampling relative to uncorrelated calculations increases with system and basis set size, and that correlated sampling greatly reduces the required number of random walkers to achieve a target statistical error. This translates to CPU-time speed-up factors of 55, 25, and 24 for the the ionization potential of the K atom, the deprotonation of methanol, and hydrogen abstraction from the O-H bond of methanol, respectively. We conclude with a discussion of further efficiency improvements that may open the door to the accurate description of chemical processes in complex systems.

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“…[110] b Ref. [111] reduced by increasing the number of random walkers, N wlk , used in the MC evaluation of the HS integral in Eq. (5).…”

Section: 0166mentioning

confidence: 99%

Chemical Transformations Approaching Chemical Accuracy via Correlated Sampling in Auxiliary-Field Quantum Monte Carlo

Shee

Zhang

Reichman

et al. 2017

J. Chem. Theory Comput.

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“…The ground state surfaces of the hydrides are known 31 to contain another minimum corresponding to the isomeric species, CH 2 XH where X=O or S.…”

Section: 6mentioning

confidence: 99%

Spectroscopy and Photochemical Dynamics of the CF₃S Radical

et al. 1997

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The CF 3 S radical has been investigated using the LIF and fluorescence depletion techniques. The vibrational structure of the first excited A 2 A 1 state has been assigned. The photodissociation process at energies above the origin of the A state has been characterized by fluorescence temporal decay and fluorescence depletion spectroscopy. Above the photodissociation threshold the ratio of the rates for the competing processes of emission and dissociation varies strongly with both energy and vibrational mode.

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“…To assign the PES bands of BrOBr and HOBr, both G2 and OVGF calculations have been performed on the ground and ionic states corresponding to ionization of the electron of different molecular orbitals in the C 2v symmetry for BrOBr and in the Cs symmetry for HOBr. The G2 procedure has been described in detail by Curtiss et al 12 The OVGF calculations are shown in Ref. 13.…”

Section: Pes Measurementmentioning

confidence: 99%

Vacuum synthesis and determination of the ionization energies of different molecular orbitals for BrOBr and HOBr

Zhimin

Sun

et al. 2003

The Journal of Chemical Physics

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Rovibrationally selected and resolved pulsed field ionization-photoelectron study of propyne: Ionization energy and spin-orbit interaction in propyne cation J. Chem. Phys. 128, 094311 (2008) Pure BrOBr and HOBr were synthesized in vacuum by heterogeneous reactions of the dried bromine vapor and Br 2 /H 2 O mixture vapors ͑5:1͒ with HgO, respectively, and then characterized by He I photoelectron spectroscopy ͑PES͒ and augmented by ab initio GAUSSIAN 2 and the outer valence Green's functional calculations. The first PE band at 10.26 eV with vibrational spacing 550Ϯ60 cm Ϫ1 and the second PE band at 11.23 eV with vibrational spacing 240Ϯ60 cm Ϫ1 are, respectively, assigned as ionizations of the electrons of the highest occupied molecular orbital ͑HOMO͒ (6b 1 (39)) and the SHOMO(13b 2 (38)) orbitals of BrOBr. The first PE band at 10.73 eV with vibrational spacing 750Ϯ60 cm Ϫ1 and the second PE band at 11.56 eV with vibrational spacing 650Ϯ60 cm Ϫ1 are, respectively, assigned as ionizations of the electrons of the HOMO(6aЉ (22)) and the SHOMO(16aЈ(21)) orbitals of HOBr. The study does not only provide vacuum synthesis conditions for preparing pure BrOBr and HOBr, but also provide experimental PES results along with theoretical ionization energies of different molecular orbitals for BrOBr and HOBr.

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Energies of CH2OH, CH3O, and related compounds

Cited by 104 publications

References 21 publications

Chemical Transformations Approaching Chemical Accuracy via Correlated Sampling in Auxiliary-Field Quantum Monte Carlo

Chemical Transformations Approaching Chemical Accuracy via Correlated Sampling in Auxiliary-Field Quantum Monte Carlo

Spectroscopy and Photochemical Dynamics of the CF₃S Radical

Vacuum synthesis and determination of the ionization energies of different molecular orbitals for BrOBr and HOBr

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Energies of CH2OH, CH3O, and related compounds

Cited by 104 publications

References 21 publications

Chemical Transformations Approaching Chemical Accuracy via Correlated Sampling in Auxiliary-Field Quantum Monte Carlo

Chemical Transformations Approaching Chemical Accuracy via Correlated Sampling in Auxiliary-Field Quantum Monte Carlo

Spectroscopy and Photochemical Dynamics of the CF3S Radical

Vacuum synthesis and determination of the ionization energies of different molecular orbitals for BrOBr and HOBr

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Product

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Spectroscopy and Photochemical Dynamics of the CF₃S Radical