The Materials Virtual Lab held its first ever retreat today. We had a great day strategizing future research directions followed by a BBQ at La Jolla Shores. We officially welcome Chi Chen, Hui Zheng, and Zhuonan Lin to the group, and congratulate Richard Tran on transiting to a graduate student!
Our article on “Data-driven First Principles Methods for the Study and Design of Alkali Superionic Conductors” has been published in Chemistry of Materials as part of an invited Methods and Protocols special topic. In this work, we provide a detailed exposition of the first principles techniques that can be used to design alkali superionic conductors, a topic of high current interest. Accompanying this article is a repository of well-documented Jupyter notebooks that allows any researcher to easily reproduce the analysis and apply the same techniques to other materials. The article is available online and the notebooks are available at the following Github repo.
We have published the world’s largest database of surface energies and Wulff shapes, dubbed Crystalium. A collaborative effort between the Materials Virtual Lab and the Materials Project, this new open-source database can help researchers design new materials for technologies in which surfaces and interfaces play an important role, such as fuel cells, catalytic converters in cars, computer microchips, nanomaterials and solid-state batteries. You can read more about it in the UCSD press release on EurekAlert! This work is published in Scientific Data as an open-access article, and Richard Tran, one of our undergraduate volunteers, is the first author.
Congrats to Zhi Deng, one of MAVRL’s founding members, on passing his Senate Exam!
In this work published in the Journal of the Electrochemical Society, we studied the effect of cold-pressing and spark-plasma sintering (SPS) processing on the Na3OBr sodium-rich anti-perovskite solid electrolytes was studied. SPS was found to reduce the interfacial impedance by 3 orders of magnitude. The much lower conductivity of Na3OBr compared to the lithium analogue is attributed to the significantly higher defect formation energies. This work is led by the Laboratory of Energy Storage and Conversion of Prof Shirley Meng. Zhi Deng and Prof Ong are co-authors.
In this follow-on work as part of the NECCESS EFRC, a combination of hard and soft x–ray photoelectron and absorption spectroscopy techniques to depth profile solid state synthesized LiVOPO4, a promising multi-electron electrode for rechargeable lithium-ion batteries. This work confirms that limited kinetics in the high voltage regime are responsible for the inability to fully intercalate 2 Li in this material. The evolution from LiVOPO4 to Li2VOPO4 via the intermediate phases as predicted in our previous work (“Thermodynamics, Kinetics and Structural Evolution of ε-LiVOPO4 over Multiple Lithium Intercalation”) is confirmed by O K–edge absorption spectroscopy and DFT calculations. Yuh-chieh Lin and Shyue Ping Ong are co-authors in this work.
Our article on “An integrated first principles and experimental investigation of the relationship between structural rigidity and quantum efficiency in phosphors for solid state lighting” has just been published in the Journal of Luminescence. This work is a collaborative effort between the McKittrick and Ong groups, and Jungmin Ha and Zhenbin Wang are co-first authors. In this work, we test the hypothesis of whether high host structural rigidity results in phosphors with high quantum efficiency, and show using an integrated approach that combines DFT calculations and experimental studies that a high Debye temperature alone is not a sufficient condition for a high quantum efficiency.
Richard Tran and Zihan Xu published their paper on “Computational study of metallic dopant segregation and embrittlement at Molybdenum grain boundaries” in Acta Materialia. Mo and its alloys are important refractory materials for high temperature applications, but suffer from low ductility. In this work, we investigated the segregation and strengthening effects of 29 metallic dopants using DFT and empirical continuum models. We show that dopant chemistry and site preference plays a significant role in segregation behavior and strengthening effects at the GBs that deviate from simple bond-breaking arguments. Ta, Re, Os and W are predicted to have a weak strengthening effect on Mo for the Σ5(310) tilt GB, and Mn, Fe, Co and Nb are predicted to have reasonable strengthening effects for the Σ5(100) twist GB. Check out the paper at our publications page.
Congratulations to Zhenbin on his first paper “Electronic Structure Descriptor for Discovery of Narrow-Band Red-Emitting Phosphors” in Chemistry of Materials! Narrow-band red-emitting phosphors are a critical component in phosphor-converted light-emitting diodes for highly efficient illumination-grade lighting. In this work, we report the discovery of a quantitative descriptor for narrow-band Eu2+-activated emission identified through a comparison of the electronic structure of known narrow-band and broad-band phosphors. By incorporating this descriptor in a high throughput first principles screening of 2,259 nitride compounds, we identify five promising new nitride hosts for Eu2+-activated red-emitting phosphors that are predicted to exhibit good chemical stability, thermal quenching resistance and quantum efficiency, as well as narrow-band emission.
Our group has recently been invited to write a comprehensive review on computational studies of solid-state alkali conductivity in rechargeable alkali-ion batteries. This article has now been published in NPG Asia Materials! Check it out at http://www.nature.com/doifinder/10.1038/am.2016.7.