Ab initio calculations of molecular properties using the orbital optimized random-phase approximation method
Final Report Abstract
This project established analytical electronic structure methods for geometry optimization and molecular properties on the level of the random phase approximation (RPA). The implemented RI-RPA yields the currently lowest scaling of the operation count, O(N4log N), and mass storage, O(N3), with system size N for energy and gradient calculations and the computational cost is comparable to that of RI-MP2 methods. The method’s results suggest that structures obtained with RPA are significantly more accurate than MP2 structures, especially for smallgap systems. Thus, RI-RPA emerges as a valuable tool for predicting minima and transition state structures of open-shell d- and f-element compounds, particularly when semi-local functionals produce wildly different results. Being robust, non-empirical, and relatively inexpensive, RI-RPA possesses many desirable features of a general purpose method that can be applied indiscriminately to a wide range of different systems and chemical environments. The vast improvement over MP2 for small-gap systems depends on the use of a noninteracting KS reference rather than HF 41 in RPA calculations. This is in line with previous observations 42 that HF-based direct RPA performs poorly for energy differences. The remaining dependence on the semi-local functional used for the KS calculation is mostly small compared to typical RPA errors, but could be reduced further by orbital optimization.
Publications
- “Analytical First-Order Molecular Properties and Forces within the Adiabatic Connection Random Phase Approximation”. J. Chem. Theory Comput. 10, 180-194 (2014)
Asbjorn M. Burow, Jefferson E. Bates, Filipp Furche, and Henk Eshuis
(See online at https://doi.org/10.1021/ct4008553)
