Software for the frontiers of quantum chemistry:An overview of developments in the Q-Chem 5 package

This article summarizes technical advances contained in the fifth major release of the Q-Chem quantum chemistry program package, covering developments since 2015. A comprehensive library of exchange–correlation functionals, along with a suite of correlated many-body methods, continues to be a hallmark of the Q-Chem software. The many-body methods include novel variants of both coupled-cluster and configuration-interaction approaches along with methods based on the algebraic diagrammatic construction and variational reduced density-matrix methods. Methods highlighted in Q-Chem 5 include a suite of tools for modeling core-level spectroscopy, methods for describing metastable resonances, methods for computing vibronic spectra, the nuclear–electronic orbital method, and several different energy decomposition analysis techniques. High-performance capabilities including multithreaded parallelism and support for calculations on graphics processing units are described. Q-Chem boasts a community of well over 100 active academic developers, and the continuing evolution of the software is supported by an “open teamware” model and an increasingly modular design

Ab initio calculations on the intramolecular electron transfer rates of a bis(hydrazine) radical cation

Electron transfer (ET) rates of a charge localized (Class II) intervalence radical cation of a bis(hydrazine) are investigated theoretically. First, the intramolecular ET parameters, i.e., reorganization energy, electronic coupling, and effective frequency, are calculated using several ab initic, approaches. And then, the extended Sumi-Marcus theory is employed to predict ET rates by using the parameters obtained. The results reveal that the rates of three isomers of [22/hex/22](+), oo(+)[22/hex/22](+), io(+)[22/hex/22](+), and oi(+)[22/hex/22](+), are agreement with the experiment quite well while the rate, of isomer ii(+)[22/hex/22](+) is about 1000 times larger than those of the others. The validity of different ab initio approaches for this system is discussed.National Nature Science Foundation of China [20773115]; National Key Basic Research Foundation Program of China [2007CB815204, 2004CB719901]; NSF [CHE-0647719