Recent News

John’s paper introducing the “rid” preconditioner for TDDFT is now available online in The Journal of Chemical Physics. This paper is the culmination of two intertwined threads in John’s research: 1) the use of semiempirical preconditioners to accelerate the convergence of ab initio TDDFT calculations; and 2) the development of the TDDFT-ris model for fast and accurate simulations of spectra. Using the rid preconditioner, TDDFT excitation energies are converged in about 5 iterations on average, which is about a factor of 3 faster than using the conventional (diagonal) preconditioner. Even more, this speedup is obtained without any loss of accuracy. The full paper is titled “Converging TDDFT calculations in 5 iterations with minimal auxiliary preconditioning”.

The group’s contribution to the cyclobutanone prediction challenge is now published online in The Journal of Chemical Physics. This paper was a true group effort, with Ericka and Sean leading the way. For this prediction challenge, groups were tasked with predicting the photochemical dynamics of cyclobutanone after being excited by 200 nm light. What made this challenge especially exciting is that all of these contributions will be stress tested by comparing to ultrafast electron diffraction experiments that were performed concurrently with the simulations. In effect, it was a double-blind experiment to definitively answer the question: “Just how predictive are our simulations, really?” The full paper is titled “Ultrafast Photochemistry and Electron Diffraction for Cyclobutanone in the S₂ State: Surface Hopping with Time-Dependent Density Functional Theory”.

John Zhou’s paper introducing the TDDFT-ris model was recently published in The Journal of Physical Chemistry Letters. In this paper, we introduce a minimal auxiliary basis set approach to approximate TDDFT using a resolution-of-the-identity approximation with just a single s-function per atom. TDDFT-ris reproduces TDDFT excited states with a mean error of about 0.06 eV while reducing the cost by a factor of 200-300. The full paper is titled “Minimal Auxiliary Basis Set Approach for the Electronic Excitation Spectra of Organic Molecules”.

Parker Group’s graduate student Ericka Roy Miller has published computational analysis supporting the synthesis and characterization of multilayer γ-graphyne, an exciting new semiconductor material. γ-graphyne is well poised to be the foundation of next generation of carbon-based devices, due to its direct band gap, ultrafast charge carrier mobility, strong physical durability, and high thermal conductivity. This work is part of an ongoing collaboration with the Rodionov Group in CWRU’s Department of Macromolecular Science and Engineering. Check it out in the Journal of the American Chemical Society, “Scalable Synthesis and Characterization of Multilayer γ-Graphyne, New Carbon Crystals with a Small Direct Band Gap”.