Two new papers from the group are now online. The first paper is a collaborative work with several other researchers here at UW: Professors David Ginger, Cody Schlenker, and Alex Jen. This was a joint synthetic, spectroscopic, and theoretical project that showed how the excited electronic dynamics of functionalized fullerenes can influence the photovoltaic performance of hybrid organic-perovskites. This work was published in Materials Horizons and can be found here.

The second paper focuses on the ability of energy-specific TDDFT (ES-TDDFT) to model core excitations in light elements. ES-TDDFT was developed in our group, but its ability to model core excitations had not been not yet been thoroughly investigated. This paper focused on the performance of several density functional and basis set combinations as well as on role of exact exchange and the importance diffuse and core basis functions. “Calibration of Energy-Specific TDDFT for Modeling K-edge XAS Spectra of Light Elements” is published in the Journal of Chemical Theory and Computation.

Congratulations to Patrick Lestrange, a second-year graduate student, on the acceptance of his paper titled “Density of States Guided Møller-Plesset Perturbation Theory” in the Journal of Chemical Theory and Computation. This paper describes a method designed to compute the correlation energy correction for large systems with high density of states, such as polymers and nanostructures. It makes use of an integral formalism using a density-of-state framework developed for Møller-Plesset perturbation theory. The paper is now available online.

Feizhi Ding’s paper published early last year titled “An efficient method for calculating dynamical hyperpolarizabilities using real-time time-dependent density functional theory” was selected for the The Journal of Chemical Physics 2013 Editors’ Choice Collection. From the JCP’s website:

The Editors at The Journal of Chemical Physics facilitate publication of the most innovative and influential articles in the field of Chemical Physics each year. In the following collection, the Editors have selected a few of the many notable JCP articles published in 2013 that present ground-breaking research. This collection represents only a small fraction of the critical research published in JCP in 2013 and is representative of the broad cross-section of topics that the journal covers. These seminal articles are freely available online until the end of 2014.

This paper was a collaborative work with Ben Van Kuiken of the Khalil group and Bruce Eichinger at the University of Washington. Feizhi employed time-domain TDDFT using the MMUT algorithm for electron dynamics developed by Xiaosong to obtain the time-dependent dipole response of a system perturbed by a monochromatic wave. By fitting each order of the time-dependent dipole response to sinusoidal waves with harmonic frequencies, he was able to obtain the corresponding (hyper)polarizabilities. The paper is now available online free until the end of 2014 and was selected as one of JCP’s Research Highlights last year.

Ongoing collaborative work with Professors Daniel R. Gamelin and David S. Ginger at the University of Washington have resulted in two new publications: “Direct Measurement of Acceptor Group Localization on Donor–Acceptor Polymers Using Resonant Auger Spectroscopy” and “Ferromagnetic excited-state Mn2+ dimers in Zn1−xMnxSe quantum dots observed by time-resolved magnetophotoluminescence“.

In the first publication, Phu Nguyen performed density functional calculations to investigate the electronic structure of the LUMO of PCPDTBT and PCDTBT, two similar donor/acceptor-type polymers. These materials are of interest for application in organic photovoltaic devices.

In the second publication, Joseph May performed density functional calculations on ZnSe nanocrystals doped with Mn2+ ions to elucidated the microscopic orbital exchange interactions that give rise to ferromagnetic coupling within photoexcited Mn2+—Mn2+ dimers.

David Lingerfelt’s paper titled “Dynamical Investigations of Inhomogenous Vibrational Broadening in Diluted Magnetic Semiconductor Nanocrystals” was just accepted for publication in the Journal of Physical Chemistry C. This is David’s first publication in the Li group and his first-ever publication in a peer-reviewed journal. Congratulations David! The paper presents a method for simulating finite-temperature, inhomogenously broadened electronic absorption spectra of large systems with high densities of states and applies the method to the problem of peak broadening in dilute magnetic semiconductor nanocrystals. The approach accurately captures the temperature-dependent inhomogeneous broadening of the charge transfer transitions and resolves previous inconsistencies between theory and experiment. The paper is now available online.

Bo Peng’s paper, titled “A Guided Self-Consistent-Field Method for Excited State Wave Function Optimization: Applications to Ligand Field Transitions in Transition Metal Complexes”, was accepted into the Journal of Chemical Theory and Computation and is now available online. The paper describes a new method that uses an eigenspace update-and-following idea to improve the SCF method for optimizing wave functions that are higher-energy solutions to the Roothaan-Hall equation. The new guided SCF method is used to optimize ligand field excited states in tetrahedral transition metal complexes, and calculate ΔSCF excitation energies. The excitation energies obtained using this method show a significant improvement over orbital energy differences and the linear response method.

Josh Goings’ first paper since joining the group (and first paper ever!) was just accepted for publication in Advances in Quantum Chemistry. The paper is titled “Accelerating Wavefunction Optimization using Quasi-Newton DIIS” and presents a new method for wavefunction optimization that incorporates the direct inversion in the iterative subspace algorithm.

The group’s productive start to the new year continues: two new publications have now been accepted! Feizhi Ding was part of a collaborative work with Alex K.-Y. Jen’s group at the University of Washington that resulted in a publication titled “Solution-Processible Highly Conducting Fullerenes” in Advanced Materials. Feizhi provided DFT calculations to probe detailed information about the electron transfer pathways in fulleropyrrolidinium ions (FPI), which were synthesized and characterized by the Jen group. The paper is now available online.

Craig Chapman’s first paper as corresponding author, titled “Solvent Effects on Intramolecular Charge Transfer Dynamics in a Fullerene Derivative,” was just accepted in the Journal of Physical Chemistry A. This paper uses the methods of real-time time-dependent density functional theory developed by the group to investigate the exciton dynamics in the C60 derivative, C60:DMA (DMA = dimethylanaline), including the solvent effects in the real-time time-dependent polarizable continuum model. The article is now available online.

Joseph May and Ryan McMorris’ paper, “Ferromagnetism in p-Type Manganese-Doped ZnO Quantum Dots”, which describes how nitrogen dopants affect the magnetic ordering of manganese unpaired spins in zinc oxide quantum dots, was just accepted into the Journal of Physical Chemistry Letters. The “Just Accepted Manuscript” is available here.