Collect. Czech. Chem. Commun. 2005, 70, 837-850

Frozen Natural Orbitals: Systematic Basis Set Truncation for Coupled-Cluster Theory

Andrew G. Taube and Rodney J. Bartlett*

Department of Chemistry, University of Florida, Quantum Theory Project, Gainesville, FL 32611, U.S.A.


The method of frozen natural orbital (FNO) basis set truncation for coupled-cluster theory is described. Numerical comparisons of the FNO potential energy surfaces of a group of small molecules at the CCSD(T) level in DZP, cc-pVTZ, cc-pVQZ bases show that truncation of up to 50% of the virtual space yields CC correlation energies that are accurate to 90 or 95% when added to the full MBPT(2) basis result. The FNO truncation method is also applied to dimethylnitramine (DMNA): both the equilibrium structure and dimer interactions, yielding results at the CCSD(T) level in both a DZP and cc-pVTZ basis set that agree with literature values. CCSD(T) calculations at two possible equilibrium structures of 1,3,5-trinitrohexahydro-1,3,5-triazine (RDX) in a truncated DZP basis are also reported.

Keywords: Coupled-cluster method; Natural orbital; Many-body perturbation theory; RDX; Reduced computational cost; FNO; Ab initio calculations; Quantum chemistry.

References: 47 live references.