State-Specific Analytical Nuclear Gradients for the Density-Fitted Exact Two-Component State-Averaged Complete Active Space Self-Consistent Field (X2C-SA-CASSCF) Theory
When a chemical system of interest contains heavy elements, it is important to obtain a balanced description of relativistic effects and electron correlation. The exact two-component (X2C) Hamiltonian includes both scalar-relativistic and spin–orbit effects with a reasonable computational cost. By using the spin–orbi...