New paper published!15 Jan 2014
I have a new paper published in the latest issue of Advances in Quantum Chemistry, called “ Self-Consistent Field using Direct Inversion in Iterative Subspace Method and Quasi-Newton Vectors”. Quite the mouthful, but hey, it is science. The idea behind the paper was to “steal” some ideas from geometry optimizations, and apply them to the problem of converging an SCF calculation (that is, a Hartree-Fock or DFT calculation). The general acceleration method for converging SCF type equations is to use an algorithm called DIIS (pronounced “dice”). Without going into the mathematics, DIIS is a way of improving your iterative guess at each step of the calculation. A really cool introduction can be found online at Dr. David Sherrill’s website. Generally, it brings a modest speed-up to your calculation, and some form of DIIS is always used nowadays in electronic structure calculations. Our twist was to use a different type of vector (a quasi-Newton vector, which gets a lot of use in geometry optimizations) to help the DIIS acceleration. Practically, we found that using a QN-DIIS method got a Hartree-Fock calculation to converge faster by a few iterations. That’s pretty cool!
You can read the paper here, but it’s probably behind a paywall for most of you. If you are really interested (it won’t hurt my feelings if you are not), feel free to email me and I’ll send you a reprint.