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Title: Efficient calculation of integrals in mixed ramp-Gaussian basis sets

Algorithms for the efficient calculation of two-electron integrals in the newly developed mixed ramp-Gaussian basis sets are presented, alongside a Fortran90 implementation of these algorithms, RAMPITUP. These new basis sets have significant potential to (1) give some speed-up (estimated at up to 20% for large molecules in fully optimised code) to general-purpose Hartree-Fock (HF) and density functional theory quantum chemistry calculations, replacing all-Gaussian basis sets, and (2) give very large speed-ups for calculations of core-dependent properties, such as electron density at the nucleus, NMR parameters, relativistic corrections, and total energies, replacing the current use of Slater basis functions or very large specialised all-Gaussian basis sets for these purposes. This initial implementation already demonstrates roughly 10% speed-ups in HF/R-31G calculations compared to HF/6-31G calculations for large linear molecules, demonstrating the promise of this methodology, particularly for the second application. As well as the reduction in the total primitive number in R-31G compared to 6-31G, this timing advantage can be attributed to the significant reduction in the number of mathematically complex intermediate integrals after modelling each ramp-Gaussian basis-function-pair as a sum of ramps on a single atomic centre.
Authors:
 [1] ;  [2]
  1. Department of Physics and Astronomy, University College London, London (United Kingdom)
  2. (Australia)
Publication Date:
OSTI Identifier:
22415595
Resource Type:
Journal Article
Resource Relation:
Journal Name: Journal of Chemical Physics; Journal Volume: 142; Journal Issue: 13; Other Information: (c) 2015 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; ALGORITHMS; CHEMISTRY; COMPARATIVE EVALUATIONS; COMPUTERIZED SIMULATION; CORRECTIONS; DENSITY FUNCTIONAL METHOD; ELECTRON DENSITY; ELECTRONS; HARTREE-FOCK METHOD; HYDROFLUORIC ACID; INTEGRALS; MOLECULES; NUCLEAR MAGNETIC RESONANCE; POTENTIALS; R CODES; REDUCTION; VELOCITY