Skip to main content

Spectroscopic accuracy directly from quantum chemistry: Application to ground and excited states of beryllium dimer

Cornell Affiliated Author(s)

Author

Sandeep Sharma
Takeshi Yanai
George Booth
C. Umrigar
Garnet Chan

Abstract

We combine explicit correlation via the canonical transcorrelation approach with the density matrix renormalization group and initiator full configuration interaction quantum Monte Carlo methods to compute a near-exact beryllium dimer curve, without the use of composite methods. In particular, our direct density matrix renormalization group calculations produce a well-depth of De = 931.2 cm-1 which agrees very well with recent experimentally derived estimates De = 929.7±2 cm-1 [J. M. Merritt, V. E. Bondybey, and M. C. Heaven, Science 324, 1548 (2009)] and De= 934.6 cm-1 [K. Patkowski, V. Špirko, and K. Szalewicz, Science 326, 1382 (2009)], as well the best composite theoretical estimates, D e = 938±15 cm-1 [K. Patkowski, R. Podeszwa, and K. Szalewicz, J. Phys. Chem. A 111, 12822 (2007)] and De=935.1±10 cm-1 [J. Koput, Phys. Chem. Chem. Phys. 13, 20311 (2011)]. Our results suggest possible inaccuracies in the functional form of the potential used at shorter bond lengths to fit the experimental data [J. M. Merritt, V. E. Bondybey, and M. C. Heaven, Science 324, 1548 (2009)]. With the density matrix renormalization group we also compute near-exact vertical excitation energies at the equilibrium geometry. These provide non-trivial benchmarks for quantum chemical methods for excited states, and illustrate the surprisingly large error that remains for 1 1Σ-g state with approximate multi-reference configuration interaction and equation-of-motion coupled cluster methods. Overall, we demonstrate that explicitly correlated density matrix renormalization group and initiator full configuration interaction quantum Monte Carlo methods allow us to fully converge to the basis set and correlation limit of the non-relativistic Schrödinger equation in small molecules. © 2014 AIP Publishing LLC.

Date Published

Journal

Journal of Chemical Physics

Volume

140

Issue

10

URL

https://www.scopus.com/inward/record.uri?eid=2-s2.0-84896333886&doi=10.1063%2f1.4867383&partnerID=40&md5=8c16f4fea398dc4c7f00a9da4bbf0486

DOI

10.1063/1.4867383

Group (Lab)

Cyrus Umrigar Group

Funding Source

NSF-CHE-1112097
NSF-CHE-1265277
1112097
1265277
25288013

Download citation