Speeding up equation of motion coupled cluster theory with the chain of spheres approximation
In the present paper, the chain of spheres exchange (COSX) approximation is applied to the highest scaling terms in the equation of motion (EOM) coupled cluster equations with single and double excitations, in particular, the terms involving integrals with four virtual labels. It is found that even the acceleration of this single term yields significant computational gains without compromising the desired accuracy of the method. For an excitation energy calculation on a cluster of five water molecules using 585 basis functions, the four virtual term is 9.4 times faster using COSX with a loose grid than using the canonical implementation, which yields a 2.6 fold acceleration for the whole of the EOM calculation. For electron attachment calculations, the four virtual term is 15 times and the total EOM calculation is 10 times faster than the canonical calculation for the same system. The accuracy of the new method was tested using Thiel’s test set for excited states using the same settings and the maximum absolute deviation over the whole test set was found to be 12.945 cm{sup −1} (59 μHartree) for excitation energies and 6.799 cm{sup −1} (31 μHartree) for electron attachments. Using MP2 amplitudes for the ground state in combinationmore »
 Authors:

;
;
^{[1]}
 MaxPlanckInstitut für Chemische Energiekonversion, Stiftstr. 3436, 45470 Mülheim an der Ruhr (Germany)
 Publication Date:
 OSTI Identifier:
 22493654
 Resource Type:
 Journal Article
 Resource Relation:
 Journal Name: Journal of Chemical Physics; Journal Volume: 144; Journal Issue: 3; Other Information: (c) 2016 AIP Publishing LLC; Country of input: International Atomic Energy Agency (IAEA)
 Country of Publication:
 United States
 Language:
 English
 Subject:
 37 INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; ACCURACY; AFFINITY; ELECTRON ATTACHMENT; ELECTRON CORRELATION; ELECTRONS; EQUATIONS OF MOTION; EXCITATION; EXCITED STATES; GAIN; GRIDS; GROUND STATES; MOLECULES; VELOCITY; WATER; YIELDS