Analytic Derivatives of Quartic-Scaling Doubly Hybrid XYGJ-OS Functional: Theory, Implementation, and Benchmark Comparison with M06-2X and MP2 Geometries for Nonbonded Complexes

• DOI: 10.1021/ct400050d
• Publication Date: 2013-03-04T22:37:55Z
• Authors: Hyunjun Ji; Yihan Shao; William A. Goddard; Yousung Jung
• Keywords: Ansatz; Benchmark (surveying); Linear scale

Analytic first derivative expression of opposite-spin (OS) ansatz adapted quartic scaling doubly hybrid XYGJ-OS functional is derived and implemented into Q-Chem. The resulting algorithm scales quartically with system size as in OS-MP2 gradient, by utilizing the combination Laplace transformation density fitting technique. performance geometry optimization assessed comparing bond lengths intermolecular properties reference coupled cluster methods. For selected nonbonded complexes S22 S66 dataset used present benchmark test, it shown that geometries are more accurate than M06-2X RI-MP2, two quantum chemical methods widely to obtain for practical systems, comparable CCSD(T) geometries.