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QM:QM embedding using electronic densities within an ONIOM framework: Energies and analytic gradients
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10.1063/1.3603450
/content/aip/journal/jcp/135/1/10.1063/1.3603450
http://aip.metastore.ingenta.com/content/aip/journal/jcp/135/1/10.1063/1.3603450

Figures

Image of FIG. 1.
FIG. 1.

Flowchart for ONIOM(QM:QM) density embedding analytic force evaluations.

Image of FIG. 2.
FIG. 2.

(a) Starting and (b) ending point geometries used in the MP2/6-31G(d):HF/6-31G potential energy surface scans of [ZnIm2(H2O)]2 + + H2O → [ZnIm2(OH)]+ + H3O+. High-level and low-level regions for ONIOM calculations are shown using ball-and-stick and tube renderings.

Image of FIG. 3.
FIG. 3.

Energy profile for the proton exchange reaction [ZnIm2(H2O)]2 + + H2O → [ZnIm2(OH)]+ + H3O+ using (a) MP2/6-31G(d):HF/6-31G and (b) B3LYP/6-31+G(d,p):HF/6-31G model chemistry combinations. Results shown include EE-AO (□), EE-fit-A (◯), and EE-fit-B (△). Curves for the high-level target (+) and low-level model chemistry (×) treating the whole system are also included.

Image of FIG. 4.
FIG. 4.

Energy profile for the proton exchange reaction [ZnIm2(H2O)]2 + + H2O → [ZnIm2(OH)]+ + H3O+ using (a) MP2/6-31G(d):HF/6-31G and (b) B3LYP/6-31+G(d,p):HF/6-31G model chemistry combinations using point charge embedding models. Results shown include mechanical embedding (□), EE-Mulliken (◯), and EE-Löwdin models. Curves for the high-level target (+) and low-level model chemistry (×) treating the whole system are also included.

Image of FIG. 5.
FIG. 5.

Structures of (a) Si8O12H7OH and (b) Si8O12H7O-. High-level and low-level regions for ONIOM calculations are shown using ball-and-stick and tube renderings.

Image of FIG. 6.
FIG. 6.

Energy (solid line) and rms force values (dashed line) as functions of geometry optimization step for the deprotonated spherosiloxane structure using the MP2/6-31G(d):HF/3-21G* model chemistry with (a) EE-AO and (b) EE-fit-A density embedding. Energy values are shown relative to the energy of the converged structure. The EE-AO density embedding optimization converged in five steps; the EE-fit-A density embedding optimization converged in eight steps.

Tables

Generic image for table
Table I.

Mean absolute deviations (kcal/mol) for the potential energy curves given by low-level, ME, EE-Mulliken, EE-Löwdin, EE-AO, EE-fit-A, and EE-fit-B models with respect to the high-level target.

Generic image for table
Table II.

Spherosiloxane deprotonation energies (kcal/mol) for various model chemistry combinations including ONIOM electronic embedding using the AO density (EE-AO), and electronic embedding using the fitted densities (EE-fit-A). See the text for model details.

Generic image for table
Table III.

Timings (in s) for mechanical embedding (ME) and electronic embedding (EE) energy plus force calculations using MP2/6-31G(d):HF/3-21G* and B3LYP/6-31G(d):BLYP/6-31G model chemistry combinations. Calculations were run on the Si8O12H7O anion.

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/content/aip/journal/jcp/135/1/10.1063/1.3603450
2011-07-06
2014-04-21
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752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: QM:QM embedding using electronic densities within an ONIOM framework: Energies and analytic gradients
http://aip.metastore.ingenta.com/content/aip/journal/jcp/135/1/10.1063/1.3603450
10.1063/1.3603450
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