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 David Lingerfelt on running that gauntlet that is the 2nd year exam. Now the entire crop of 2nd years passed their exams. His research presentation focused on vibronic broadening of absorption spectra.

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.

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.

The Li group welcomes Katherine Lacy and Winston Wright to the lab.

Katherine joins us from Willamette University in Salem, Oregon where she is a junior in the mathematics department with a minor in chemistry. Katherine joins the group as part of the Amgen Scholars Summer Research Program in Science and Biotechnology. The program “provides hundreds of selected undergraduate students with the opportunity to engage in hands-on research experience at some of the nation’s leading educational institutions.” During the 9-week program, Katherine will work with graduate student David Lingerfelt to apply nonadiabatic molecular dynamics simulations to study the isomerization of azobenzene.

Winston joins us from Interlake High School in Bellevue, Washington where he is a member of his school’s math club. Winston will be applying his skills in mathematics, which helped him to win third place at this year’s Vex Robotics World Championship, to the study of the discrete variable representation (DVR) and its application in modeling quantum proton dynamics.

Again, welcome Katherine and Winston. Enjoy the beautiful Seattle summer!

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.

The group’s first publication of the new year is now available online. Feizhi Ding was part of a collaborative work with Ben Van Kuiken of the Khalil group and Bruce Eichinger at the University of Washington that resulted in a publication titled “An efficient method for calculating dynamical hyperpolarizabilities using real-time time-dependent density functional theory” in The Journal of Chemical Physics. 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 and was selected as one of JCP’s Research Highlights.

The result of a productive summer: three new publications now available online! Joseph May and Jeremy Lehner’s paper, titled “Transition State Search Using a Guided Direct Inversion in the Iterative Subspace Method,” was just published in the Journal of Chemical Theory and Computation. This paper presents a hybrid geometry optimization method for locating transition states combining the power of RFO and DIIS methods while making use of the unique nature of the transition state of a molecule. The paper is available online.

Phu Nguyen, Feizhi Ding, and Sean Fischer’s paper, titled “Solvated First-Principles Excited-State Charge-Transfer Dynamics with Time-Dependent Polarizable Continuum Model and Solvent Dielectric Relaxation,” was just published in the Journal of Physical Chemistry Letters. This paper describes an exciting new method in which the solvent implicit reaction field is coupled to the time-dependent electronic density of the solute molecule allowing the study of solvent effects on the dynamics of charge-transfer processes. The paper is available online.

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 “Improved Charge Transport and Absorption Coefficient in Indacenodithieno[3,2-b]thiophene-based Ladder-Type Polymer Leading to Highly Efficient Polymer Solar Cells” in Advanced Materials. Feizhi provided DFT calculations to probe detailed information about oscillator strength, optimized geometry, and wave-function distribution of PIDT-DFBT and PIDTT-DFBT polymers, which were synthesized and characterized by the Jen group. The paper is now available online.

Feizhi Ding and Craig Chapman’s paper, titled “Mechanisms of bridge-mediated electron transfer: A TDDFT electronic dynamics study,” was just published in the Journal of Chemical Physics. This paper presents the results of using full Ehrenfest dynamics with nuclear motion to probe the dynamics of electron transfer in a donor-bridge-acceptor polyene dye scaffold. The paper is available online.

Today, the Li group says farewell to Dr. Wenkel Liang, who successfully defended his Ph.D. dissertation titled “From Geometry Optimization to Time Dependent Molecular Structure Modeling: Method Developments, ab initio Theory and Applications” last month. Wenkel joined the research group in 2004 and has worked on numerous application and development projects resulting in 18 publications with Prof. Li, a group record! Wenkel will be missed, especially for his technical savvy, having been the group’s expert Gaussian coder and administrator for the chemistry department’s computer clusters. Wenkel will return home to Chengdu, China for a couple of months to visit friends and family. In July, he heads to Simulations Plus Inc. in Lancaster, California to begin work on applications using artificial neural networks ensembles (ANNE).