Quantum Monte Carlo study of singlet–triplet transition in ethylene

Akramine, Ouafae El; Kollias, A. C.; Lester, William A.

doi:10.1063/1.1579466

Cited by 28 publications

(28 citation statements)

References 48 publications

(33 reference statements)

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“…Although there does not appear to be sufficient experimental data to make a good comparison, we do have the recent high quality CCSD͑T͒/CBS result 45 of 68.8 kcal/mol to compare against, and with which our recommended result of 69.20Ϯ 0.17 kcal/ mol only differs by 0.4 kcal/mol. El Akramine and co-workers 43 also recently studied this transition using QMC to obtain 69.6Ϯ 0.3 kcal/ mol, and our results are in agreement with theirs, even given the differences in our wave functions.…”

Section: B Ethylenesupporting

confidence: 78%

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Generalized valence bond wave functions in quantum Monte Carlo

Anderson

Goddard

2010

The Journal of Chemical Physics

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We present a technique for using quantum Monte Carlo ͑QMC͒ to obtain high quality energy differences. We use generalized valence bond ͑GVB͒ wave functions, for an intuitive approach to capturing the important sources of static correlation, without needing to optimize the orbitals with QMC. Using our modifications to Walker branching and Jastrows, we can then reliably use diffusion quantum Monte Carlo to add in all the dynamic correlation. This simple approach is easily accurate to within a few tenths of a kcal/mol for a variety of problems, which we demonstrate for the adiabatic singlet-triplet splitting in methylene, the vertical and adiabatic singlet-triplet splitting in ethylene, 2 + 2 cycloaddition, and Be 2 bond breaking.

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Section: B Ethylenesupporting

confidence: 78%

“…41͒ to 4.6 eV. 42 Calculations have been in better agreement, with results ranging from recent QMC calculations 43,44 both producing 4.50Ϯ 0.02 and 4.51 eV for a CCSD͑T͒/CBS ͑Ref. 45͒ calculation, up to about 4.6 eV for MRCI ͑Ref.…”

Section: B Ethylenesupporting

confidence: 60%

Generalized valence bond wave functions in quantum Monte Carlo

Anderson

Goddard

2010

The Journal of Chemical Physics

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“…In addition to the heat of formation, Nguyen et al 61 reported both vertical (104.1 kcal/mol) and adiabatic (65.6 kcal/mol) excitation energies for the triplet state. Corresponding diffusion Monte Carlo values of 103.5 ± 0.3 kcal/mol (vertical) and 66.4 ± 0.3 kcal/mol (adiabatic) were obtained by El Akramine et al 54 Our best composite adiabatic excitation energy ( 1 A g → 3 A 1 ) is 65.8 ± 0.6 kcal/mol, where the estimated uncertainty assumes the worst case scenario of no cancellation of error in the energy estimates for each state.…”

Section: Twisted 3 a 1 Statementioning

confidence: 55%

A systematic approach to vertically excited states of ethylene using configuration interaction and coupled cluster techniques

Feller

Peterson

Davidson

2014

The Journal of Chemical Physics

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A systematic sequence of configuration interaction and coupled cluster calculations were used to describe selected low-lying singlet and triplet vertically excited states of ethylene with the goal of approaching the all electron, full configuration interaction/complete basis set limit. Included among these is the notoriously difficult, mixed valence/Rydberg (1)B(1u) V state. Techniques included complete active space and iterative natural orbital configuration interaction with large reference spaces which led to variational spaces of 1.8 × 10(9) parameters. Care was taken to avoid unintentionally biasing the results due to the widely recognized sensitivity of the V state to the details of the calculation. The lowest vertical and adiabatic ionization potentials to the (2)B(3u) and (2)B3 states were also determined. In addition, the heat of formation of twisted ethylene (3)A1 was obtained from large basis set coupled cluster theory calculations including corrections for core/valence, scalar relativistic and higher order correlation recovery.

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“…From the energies 44 calculated at the CCSD(T)/6-311+G(3df,2p)//QCISD/6-311G(d,p) level, a value of ∆E S-T (C 2 H 4 ) ) 64.5 kcal/mol can be derived, including a ZPE correction of 3.2 kcal/mol. Lester and coworkers 45 carried out diffusion Monte Carlo (DMC) calculations on the ground state singlet and first excited triplet state of ethylene at the MP2/6-311++G** geometries, with trial functions constructed from Hartree-Fock, complete active space self-consistent field, and multiconfigurational self-consistent field wavefunctions. Total atomization energies (TAEs) were calculated for the singlet and triplet states at these optimized geometries.…”

Section: Introductionmentioning

confidence: 99%

Heats of Formation of Triplet Ethylene, Ethylidene, and Acetylene

et al. 2007

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Heats of formation of the lowest triplet state of ethylene and the ground triplet state of ethylidene have been predicted by high level electronic structure calculations. Total atomization energies obtained from coupledcluster CCSD(T) energies extrapolated to the complete basis set limit using correlation consistent basis sets (CBS), plus additional corrections predict the following heats of formation in kcal/mol: ∆H f 0 (C 2 H 4 , 3 A 1 ) )80.1 at 0 K and 78.5 at 298 K, and ∆H f 0 (CH 3 CH, 3 A′′) ) 86.8 at 0 K and 85.1 at 298 K, with an error of less than (1.0 kcal/mol. The vertical and adiabatic singlet-triplet separation energies of ethylene were calculated as ∆E S-T,vert ) 104.1 and ∆E S-T,adia ) 65.8 kcal/mol. These results are in excellent agreement with recent quantum Monte Carlo (DMC) values of 103.5 ( 0.3 and 66.4 ( 0.3 kcal/mol. Both sets of computational values differ from the experimental estimate of 58 ( 3 kcal/mol for the adiabatic splitting. The computed singlet-triplet gap at 0 K for acetylene is ∆E S-T,adia (C 2 H 2 ) ) 90.5 kcal/mol, which is in notable disagreement with the experimental value of 82.6 kcal/mol. The heat of formation of the triplet is ∆H f 0 (C 2 H 2 , 3 B 2 ) ) 145.3 kcal/mol. There is a systematic underestimation of the singlet-triplet gaps in recent photodecomposition experiments by ∼7 to 8 kcal/mol. For vinylidene, we predict ∆H f 0 (H 2 CC, 1 A 1 ) ) 98.8 kcal/mol at 298 K (exptl. 100.3 ( 4.0), ∆H f 0 (H 2 CC, 3 B 2 ) ) 146.2 at 298 K, and an energy gap ∆E S-T-adia (H 2 CC) ) 47.7 kcal/ mol.

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Quantum Monte Carlo study of singlet–triplet transition in ethylene

Cited by 28 publications

References 48 publications

Generalized valence bond wave functions in quantum Monte Carlo

Generalized valence bond wave functions in quantum Monte Carlo

A systematic approach to vertically excited states of ethylene using configuration interaction and coupled cluster techniques

Heats of Formation of Triplet Ethylene, Ethylidene, and Acetylene

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