An explicitly correlated functional form for expanding the wave function of an $N$-particle system with arbitrary angular momentum and parity is presented. We develop the projection-based approach, numerically exploited in our previous work [J. Muolo, E. Mátyus, and M. Reiher, J. Chem. Phys. 149, 184105 (2018)], to explicitly correlated Gaussian functions with one-axis-shifted centers and derive the matrix elements for the Hamiltonian and the angular momentum operators by analytically solving the integral projection operator. Variational few-body calculations without assuming the Born-Oppenheimer approximation are presented for several rotationally excited states of three- and four-particle systems. We show how the formalism can be used as a unified framework for high-accuracy calculations of properties of small atoms and molecules.

• Received 30 April 2020
• Accepted 29 June 2020

DOI:https://doi.org/10.1103/PhysRevA.102.022803