Symmetric dissociation of the water molecule with truncation energy error. A benchmark study

Abstract

We use selected CI with truncation energy error to study the symmetric dissociation of H2O with two triple zeta quality bases. In both cases, the difference between CBS energy errors at the equilibrium geometry and dissociation is larger than 10 mH thus chemically accurate NPE values do not guarantee a chemically accurate PES.

Frozen-Core versus Fully-Correlated Configuration Interaction on the Ground and Lowest Excited States of N+ and N

“…where ∆E OBI µ is the error due to orbital basis incompleteness (OBI) [9], and ∆E CI µ represents the error due to any simplification of the frozen-core CI (FCI) computation effected in the evaluation of E nr µ [10]. Calculation of FCI energy, even with a small system, is computationally difficult due to the huge CI size.…”