| Autor: |
Hartman JD; Department of Chemistry, University of California, Riverside, California 92521, USA., Monaco S; The Pennsylvania State University, The Eberly Campus, 2201 University Dr, Lemont Furnace, Pennsylvania 15456, USA., Schatschneider B; The Pennsylvania State University, The Eberly Campus, 2201 University Dr, Lemont Furnace, Pennsylvania 15456, USA., Beran GJ; Department of Chemistry, University of California, Riverside, California 92521, USA. |
| Jazyk: |
angličtina |
| Zdroj: |
The Journal of chemical physics [J Chem Phys] 2015 Sep 14; Vol. 143 (10), pp. 102809. |
| DOI: |
10.1063/1.4922649 |
| Abstrakt: |
We assess the quality of fragment-based ab initio isotropic (13)C chemical shift predictions for a collection of 25 molecular crystals with eight different density functionals. We explore the relative performance of cluster, two-body fragment, combined cluster/fragment, and the planewave gauge-including projector augmented wave (GIPAW) models relative to experiment. When electrostatic embedding is employed to capture many-body polarization effects, the simple and computationally inexpensive two-body fragment model predicts both isotropic (13)C chemical shifts and the chemical shielding tensors as well as both cluster models and the GIPAW approach. Unlike the GIPAW approach, hybrid density functionals can be used readily in a fragment model, and all four hybrid functionals tested here (PBE0, B3LYP, B3PW91, and B97-2) predict chemical shifts in noticeably better agreement with experiment than the four generalized gradient approximation (GGA) functionals considered (PBE, OPBE, BLYP, and BP86). A set of recommended linear regression parameters for mapping between calculated chemical shieldings and observed chemical shifts are provided based on these benchmark calculations. Statistical cross-validation procedures are used to demonstrate the robustness of these fits. |
| Databáze: |
MEDLINE |
| Externí odkaz: |
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