Hylleraas–Configuration Interaction calculations on the 11S ground state of helium atom

 

María Belén Ruiz

Pages 3340-3361 | Received 07 Apr 2015, Accepted 29 May 2015, Accepted author version posted online: 29 Jun 2015, Published online: 24 Jul 2015

 

 

Abstract

Hylleraas–Configuration Interaction (Hy–CI) calculations on the ground 1¹S state of helium atom are presented using s-, p-, d-, and f-Slater orbitals of both real and complex form. Techniques of construction of adapted configurations, optimization of the orbital exponents, and structure of the wave function expansion are explored. A new method to evaluate the two-electron kinetic energy integrals occurring in the Hy–CI method has been tested in this work and compared with other methods. The non-relativistic Hy–CI energy values are ≈10 picohartree accurate, about 2.2 × 10⁻⁶ cm⁻¹. The Hy–CI calculations are compared with Configuration Interaction (CI) and Hylleraas (Hy) calculations employing the same orbital basis set, same computer code, and same computer machines. The computational required times are reported.

 https://sci-hub.se/https://doi.org/10.1080/00958972.2015.1064907