0000000000563805
AUTHOR
Keld L. Bak
showing 4 related works from this author
The Dalton quantum chemistry program system
2013
Dalton is a powerful general-purpose program system for the study of molecular electronic structure at the Hartree-Fock, Kohn-Sham, multiconfigurational self-consistent-field, MOller-Plesset, confi ...
Coupled-cluster singles, doubles and triples (CCSDT) calculations of atomization energies
2000
Atomization energies have been calculated for CO, H2O, F-2, HF, N-2 and CH2 (the (1)A(1) state) using the coupled-duster singles, doubles and triples (CCSDT) model as well as the coupled-cluster singles and doubles model with a perturbative correction for triples [CCSD(T)]. TheCCSD(T) model provides an excellent approximation to the CCSDT model; at the cc-pV5Z basis set level, the CCSDT valence triples contribution is underestimated by 9.1% (0.8 kJ/mol) for CH, and overestimated for the remaining molecules by as little as 4.3%(1.3 kJ/mol) for F-2,and as much as 8.4% (3.0 kJ/mol) for N-2. At the CCSDT level, the agreement with experiment is not improved, suggesting that some cancellation of …
The accuracy of molecular dipole moments in standard electronic structure calculations
2000
Abstract A systematic investigation has been carried out of the accuracy of calculated molecular equilibrium dipole moments of 11 polar closed-shell molecules, using the HF, MP2, CCSD and CCSD(T) models and correlation-consistent basis sets. Augmented basis sets are important for improving the basis-set convergence, but the quality of the results depends more on the correlation treatment than on the cardinal number of the basis set. Augmented triple-zeta basis sets are sufficient for most calculations. The mean absolute error of the HF calculations is 0.16 D, which is reduced at the MP2 and CCSD levels to 0.048 and 0.025 D, respectively. The CCSD(T) errors are small – typically
Molecular equilibrium structures from experimental rotational constants and calculated vibration–rotation interaction constants
2002
A detailed study is carried out of the accuracy of molecular equilibrium geometries obtained from least-squares fits involving experimental rotational constants B(0) and sums of ab initio vibration-rotation interaction constants alpha(r)(B). The vibration-rotation interaction constants have been calculated for 18 single-configuration dominated molecules containing hydrogen and first-row atoms at various standard levels of ab initio theory. Comparisons with the experimental data and tests for the internal consistency of the calculations show that the equilibrium structures generated using Hartree-Fock vibration-rotation interaction constants have an accuracy similar to that obtained by a dir…