1887
banner image
No data available.
Please log in to see this content.
You have no subscription access to this content.
No metrics data to plot.
The attempt to load metrics for this article has failed.
The attempt to plot a graph for these metrics has failed.
Assessing the accuracy of quantum Monte Carlo and density functional theory for energetics of small water clusters
Rent:
Rent this article for
USD
10.1063/1.4730035
/content/aip/journal/jcp/136/24/10.1063/1.4730035
http://aip.metastore.ingenta.com/content/aip/journal/jcp/136/24/10.1063/1.4730035

Figures

Image of FIG. 1.
FIG. 1.

Errors of DFT and DMC distortion energy of the H2O monomer for a thermal sample of 100 configurations (see text). Quantities shown are deviations of calculated energies from Partridge-Schwenke benchmark values with PBE (black pluses), BLYP (purple triangles), B3LYP (green diamonds) and PBE0 (red crosses), and with DMC (black squares) plotted against the PS distortion energy itself. Units: mE h.

Image of FIG. 2.
FIG. 2.

Errors of DMC and DFT approximations relative to CCSD(T) benchmarks for total energies of thermal sample of 198 dimer configuration, plotted vs O–O distance. Symbols represent PBE (black pluses), BLYP (purple triangles), B3LYP (green diamonds), PBE0 (red crosses) and DMC (black squares). Units: mE h.

Image of FIG. 3.
FIG. 3.

Errors of DFT approximations for total energies of thermal sample of 198 dimer configurations when 1-body part is corrected by replacing the DFT 1-body energy by the essentially exact Partridge-Schwenke function. As in Fig. 2, errors are relative to CCSD(T) benchmarks and are plotted vs O–O distance. Symbols represent PBE (black pluses), BLYP (purple triangles), B3LYP (green diamonds) and PBE0 (red crosses). Errors of DMC (black squares) are shown for comparison. Units: mE h.

Image of FIG. 4.
FIG. 4.

Errors of DFT and DMC total energy of the H2O trimer for a thermal sample of 50 configurations drawn from a classical simulation of liquid water (see text). Quantities shown are deviations of calculated energies from CCSD(T) benchmark energies near the basis-set limit, with PBE (black pluses), BLYP (purple triangles), B3LYP (green diamonds) and PBE0 (red crosses), and with DMC (black squares) plotted against the benchmark energy itself. Units: mE h.

Image of FIG. 5.
FIG. 5.

Errors of DFT and DMC total energy of the H2O pentamer for a thermal sample of 25 configurations drawn from a classical simulation of liquid water (see text). Quantities shown are deviations of calculated energies from CCSD(T) benchmark energies near the basis-set limit, with PBE (black pluses), BLYP (purple triangles), B3LYP (green diamonds) and PBE0 (red crosses), and with DMC (black squares) plotted against the benchmark energy itself. Units: mE h.

Image of FIG. 6.
FIG. 6.

Comparison of DFT values of 2-body energies (upper panel) and 3-body energies (lower panel) of four isomers of the H2O hexamer with benchmark values from CCSD(T). Numbering of isomers is prism: 1, cage: 2, book: 3, ring: 4. Units: mE h.

Tables

Generic image for table
Table I.

Mean values and rms fluctuations of DMC and DFT errors of monomer energy for a thermal sample of 100 configurations (see text). The Partridge-Schwenke energy function is used as the “exact” energy, and the energy zero for DMC and DFT approximations is taken to be the energy in the PS equilibrium geometry. Units: mE h.

Generic image for table
Table II.

Comparison of DMC energies and DFT energies given by the PBE, BLYP, B3LYP, and PBE0 functionals with CCSD(T) benchmarks for the 10 stationary points of the H2O dimer. For each set of energies, the zero of energy has been taken so that the energy of the global minimum geometry is equal to zero. Numbering of stationary points follows that of previous authors (see, e.g., Ref. 31). Energy units: mE h.

Generic image for table
Table III.

DMC and DFT mean and rms fluctuation of errors of the total energy for thermal sample of 198 dimer configurations. In the case of DFT, the approximations denoted by PBE-Δ1 etc. represent the total energy after correction for errors of the 1-body energy (see text). Units: mE h.

Generic image for table
Table IV.

Deviations of energies given by corrected DFT approximations away from CCSD(T) benchmark energies for thermal samples of (H2O) n 3 ⩽ n ⩽ 6 configurations. Notations DFT, DFT-Δ1, and DFT-Δ12 indicate DFT approximations uncorrected, corrected for 1-body errors, and corrected for both 1- and 2-body errors. Each entry gives the mean deviation, with rms fluctuation of the deviation in parentheses. Mean and rms deviations of DMC energies away from CCSD(T) benchmarks are shown for comparison. Energy units: mE h per water monomer.

Generic image for table
Table V.

Total energies of selected isomers of the water hexamer relative to that of the prism, calculated by different methods. In all cases, the geometry of the isomer is the relaxed geometry given by MP2 calculations with the AVTZ basis, as given in the supplementary information of Ref. 61. All energies were calculated in the present work, except for the MP2 and CCSD(T) energies marked with † from Ref. 37 and the DMC energies from Ref. 61. Entries DFT-n with n = 2 and 3 are DFT energies corrected for 1- and 2-body errors, and corrected for 1-, 2- and 3-body errors, respectively. Values in parentheses represent errors compared with the CCSD(T) energies from Ref. 37. Energy units: mE h.

Loading

Article metrics loading...

/content/aip/journal/jcp/136/24/10.1063/1.4730035
2012-06-25
2014-04-19
Loading

Full text loading...

This is a required field
Please enter a valid email address
752b84549af89a08dbdd7fdb8b9568b5 journal.articlezxybnytfddd
Scitation: Assessing the accuracy of quantum Monte Carlo and density functional theory for energetics of small water clusters
http://aip.metastore.ingenta.com/content/aip/journal/jcp/136/24/10.1063/1.4730035
10.1063/1.4730035
SEARCH_EXPAND_ITEM