ECP Calculations

ECP Calculation — Iodine Atom (LANL2DZ)

task: RHF STO-3G

GEOMETRY
  I  0.0  0.0  0.0
END

BASIS
  Library STO-3G
  Ecp     lanl2dz
END

Notes

• The Ecp field in the BASIS section is the supported way to attach an ECP library to a calculation.
• Available ECP libraries: LANL2DZ, Stuttgart (SDD), and others.
• ECPs replace core electrons with an effective potential, reducing the number of basis functions for heavy elements.
• The ECP contribution is added to the core Hamiltonian automatically.

Usage

BASIS
  Library def2-TZVP
  Ecp lanl2dz
END

The basis set Library specifies the valence basis; Ecp specifies the effective core potential. Both are required for ECP calculations.