Abstract
The ability to accurately calculate reaction barrier heights is of central importance to many areas of chemistry. We report an extensive study examining the basis set convergence of post-CCSD(T) contributions (up to CCSDT(Q)) for a diverse set of 28 reaction barrier heights. In contrast to previous studies, we focus here on larger transition structures (TSs) involving 4-7 non-hydrogen atoms. The set of reaction barrier heights includes pericyclic, bipolar cycloaddition, cycloreversion, and multiple-proton transfer reactions. We find that in most cases post-CCSD(T) contributions converge rapidly toward the basis set limit, such that even double-zeta and truncated double-zeta basis sets provide useful estimates of the T-(T) and (Q) contributions, respectively. In addition, we find that due to the tendency of these small basis sets to systematically underestimate the T-(T) and (Q) components, scaling is an effective approach for improving performance. For example, scaling the T-(T)/cc-pVDZ contribution by 1.25 results in an RMSD of merely 0.4 kJ mol(-1) relative to basis set limit reference values from W3lite-F12 theory. Similarly, calculating the (Q) contribution with a cc-pVDZ basis set without d functions and scaling by 1.6 results in an RMSD of 0.5 kJ mol(-1). We also examine the magnitude of post-CCSD(T) contributions for a wide range of TSs. We find that for pericyclic, bipolar cycloaddition, and multiple-proton transfer reactions there is an effective cancellation between the T-(T) and (Q) components (i.e., they have opposite signs and are of similar magnitude), such that overall post-CCSD(T) contributions to the reaction barrier heights are below similar to 1 kJ mol(1) (in absolute value). However, for the barrier heights of cycloreversion reactions, the T-(T) and (Q) components are both negative and large and consequentially post-CCSD(T) contributions reduce the reaction barrier heights by significant amounts ranging between 4.1 and 6.7 kJ mol(-1).
| Original language | English |
|---|---|
| Pages (from-to) | 6720-6732 |
| Number of pages | 13 |
| Journal | Journal of Physical Chemistry A |
| Volume | 123 |
| Issue number | 31 |
| DOIs | |
| Publication status | Published - 8 Aug 2019 |
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Highly Accurate CCSDT(Q)/CBS Reaction Barrier Heights for a Diverse Set of Transition Structures : Basis Set Convergence and Cost-Effective Approaches for Estimating Post-CCSD(T) Contributions. / Karton, Amir.
In: Journal of Physical Chemistry A, Vol. 123, No. 31, 08.08.2019, p. 6720-6732.Research output: Contribution to journal › Article
TY - JOUR
T1 - Highly Accurate CCSDT(Q)/CBS Reaction Barrier Heights for a Diverse Set of Transition Structures
T2 - Basis Set Convergence and Cost-Effective Approaches for Estimating Post-CCSD(T) Contributions
AU - Karton, Amir
PY - 2019/8/8
Y1 - 2019/8/8
N2 - The ability to accurately calculate reaction barrier heights is of central importance to many areas of chemistry. We report an extensive study examining the basis set convergence of post-CCSD(T) contributions (up to CCSDT(Q)) for a diverse set of 28 reaction barrier heights. In contrast to previous studies, we focus here on larger transition structures (TSs) involving 4-7 non-hydrogen atoms. The set of reaction barrier heights includes pericyclic, bipolar cycloaddition, cycloreversion, and multiple-proton transfer reactions. We find that in most cases post-CCSD(T) contributions converge rapidly toward the basis set limit, such that even double-zeta and truncated double-zeta basis sets provide useful estimates of the T-(T) and (Q) contributions, respectively. In addition, we find that due to the tendency of these small basis sets to systematically underestimate the T-(T) and (Q) components, scaling is an effective approach for improving performance. For example, scaling the T-(T)/cc-pVDZ contribution by 1.25 results in an RMSD of merely 0.4 kJ mol(-1) relative to basis set limit reference values from W3lite-F12 theory. Similarly, calculating the (Q) contribution with a cc-pVDZ basis set without d functions and scaling by 1.6 results in an RMSD of 0.5 kJ mol(-1). We also examine the magnitude of post-CCSD(T) contributions for a wide range of TSs. We find that for pericyclic, bipolar cycloaddition, and multiple-proton transfer reactions there is an effective cancellation between the T-(T) and (Q) components (i.e., they have opposite signs and are of similar magnitude), such that overall post-CCSD(T) contributions to the reaction barrier heights are below similar to 1 kJ mol(1) (in absolute value). However, for the barrier heights of cycloreversion reactions, the T-(T) and (Q) components are both negative and large and consequentially post-CCSD(T) contributions reduce the reaction barrier heights by significant amounts ranging between 4.1 and 6.7 kJ mol(-1).
AB - The ability to accurately calculate reaction barrier heights is of central importance to many areas of chemistry. We report an extensive study examining the basis set convergence of post-CCSD(T) contributions (up to CCSDT(Q)) for a diverse set of 28 reaction barrier heights. In contrast to previous studies, we focus here on larger transition structures (TSs) involving 4-7 non-hydrogen atoms. The set of reaction barrier heights includes pericyclic, bipolar cycloaddition, cycloreversion, and multiple-proton transfer reactions. We find that in most cases post-CCSD(T) contributions converge rapidly toward the basis set limit, such that even double-zeta and truncated double-zeta basis sets provide useful estimates of the T-(T) and (Q) contributions, respectively. In addition, we find that due to the tendency of these small basis sets to systematically underestimate the T-(T) and (Q) components, scaling is an effective approach for improving performance. For example, scaling the T-(T)/cc-pVDZ contribution by 1.25 results in an RMSD of merely 0.4 kJ mol(-1) relative to basis set limit reference values from W3lite-F12 theory. Similarly, calculating the (Q) contribution with a cc-pVDZ basis set without d functions and scaling by 1.6 results in an RMSD of 0.5 kJ mol(-1). We also examine the magnitude of post-CCSD(T) contributions for a wide range of TSs. We find that for pericyclic, bipolar cycloaddition, and multiple-proton transfer reactions there is an effective cancellation between the T-(T) and (Q) components (i.e., they have opposite signs and are of similar magnitude), such that overall post-CCSD(T) contributions to the reaction barrier heights are below similar to 1 kJ mol(1) (in absolute value). However, for the barrier heights of cycloreversion reactions, the T-(T) and (Q) components are both negative and large and consequentially post-CCSD(T) contributions reduce the reaction barrier heights by significant amounts ranging between 4.1 and 6.7 kJ mol(-1).
KW - CORRELATED MOLECULAR CALCULATIONS
KW - GAUSSIAN-BASIS SETS
KW - PERICYCLIC-REACTIONS
KW - COMPUTATIONAL THERMOCHEMISTRY
KW - 1,3-DIPOLAR CYCLOADDITIONS
KW - ACTIVATION BARRIERS
KW - REACTION ENERGETICS
KW - CBS-QB3 METHODS
KW - STANDARD SET
KW - AB-INITIO
U2 - 10.1021/acs.jpca.9b04611
DO - 10.1021/acs.jpca.9b04611
M3 - Article
VL - 123
SP - 6720
EP - 6732
JO - The Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory
JF - The Journal of Physical Chemistry Part A: Molecules, Spectroscopy, Kinetics, Environment and General Theory
SN - 1089-5639
IS - 31
ER -