arXiv subjects

Mark Earl Casida

Publications and source records attributed to Mark Earl Casida.

4 recordsLinked to original sources

arXiv2026

Axel Dieter Becke: Not just the "B" in "B3LYP"

There is hardly anyone doing electronic structure calculations on molecules who has not used the famous B3LYP functional. Many will even know that the "B" in B3LYP stands for Becke, but how many know the history of the B3LYP functional? Behind this functional, Axel Becke has two of the most highly cited papers in both chemistry and physics---both with several tens of thousands of citations---and many less cited, but arguably equally important accomplishments, that led to B3LYP, as well as continued developments in building ever better density-functional approximatons after the appearance of B3LYP. Axel has received much recognition and many honors for his work. In particular, in 2015, Axel was awarded Canada's highest honor for science and engineering---namely the Gerhard Herzberg Gold Medal. Achievements like this require more than "just" brilliance; they require being the right person in the right place at the right time. I will argue that Axel did indeed fulfill these requirements. At the same time, I will try to give some flavor of the field of electronic structure as seen through my own eyes and those of a few others during the period from the beginning of Axel's career up until very recent times.

physics.chem-ph↗

arXiv2020

Modeling the Physical Properties of Environmentally-Friendly Optical Magnetic Switches: DFT and TD-DFT

The dominant majority of the hundreds of available spin-crossover compounds, including the technologically most promising ones, are based on the Earth-abundant metal iron, making these switches particularly appealing in terms of sustainable technology. Furthermore, it has recently been established that these materials may be synthesized using the techniques of Green Chemistry. Spin crossover in transition metal complexes can be induced by a change of temperature, by the application of an external pressure, or a magnetic field, and also by photoexcitation. Given the wide variety of functionalities to which these bistable photomagnetic systems could give access, they may be viewed as the prototypes of molecular-scale optomagnetic switches. Hence, in response to the growing demand for storing and treating increasingly-dense information, much effort has been devoted over several decades to the design of transition metal materials exhibiting spin crossover in technologically-accessible temperature ranges. The cornerstone for designing new efficient photoactive spin-crossover materials remains the ability to predict the magnetic behaviour and the photoresponse of any first-row transition complex, and the manner in which its properties are influenced by its environment. This is a challenge for the inorganic chemist and also, most notably, for the theoretical and the computational chemist. This chapter gives an overview of the issues tied to the application of DFT and TD-DFT to the characterisation of transition metal complexes in the framework of spin-crossover and related phenomena.

cond-mat.other↗

arXiv2020

Computational Studies of Ruthenium and Iridium Complexes for Energy Sciences and Progress on Greener Alternatives

The energy sciences attempt to meet the increasing world-wide need for energy, as well as sustainability goals, by cleaner sources of energy, by new alternative sources of energy, and by more efficient uses of available energy. These goals are entirely consistent with the principles of green chemistry. This chapter concerns devices for creating electricity from light and for creating light from electricity. The major focus is on the photoproperties of ruthenium and iridium complexes, which have been proven to be a rich source of inspiration for conceiving photoactivated devices, including organic photovoltaic (OPV) cells and organic light emitting diodes (OLEDs). The chapter reviews important already-in-use and potential applications of ruthenium and iridium complex-based photodevices, including the underlying mechanism behind their functioning and its investigation through computational chemistry approaches. It highlights the role of the information obtained from computational studies for the design of more efficient photodevices. The final part complements the discourse with a review of the progress on greener alternatives for OPVs and OLEDs.

physics.chem-ph↗

arXiv2011

Real-Time Dynamics and Conical Intersections

This book chapter is a general introduction to photo-dynamics. An outlined structure to the theoretical studies on classical/quantum/mixed dynamics were described from the literature point of view. Such methods get constrained for the practical applications due to parametrizations/computational cost. As an alternate TDDFT-based dynamics studies are promising. we have shown that the TDDFT calculations could be as accurate as high quality monte-carlo calculations and the reliability of the TDDFT calculations for locating the conical intersection through the simple ring-opening reaction of oxirane. Pros and cons of TDDFT for photo-dynamics calculations have been presented for the development of this fast evolving field.

cond-mat.other↗