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.

Subjects in China, Japan, and the United States reported probability judgments. In Study 1, Chinese and American subjects indicated degrees of certainty about their answers to general-knowledge questions with discrete alternatives, e.g., whether potatoes grow better in warm or in cool climates. In Study 2, Japanese subjects made similar discrete-alternative assessments. In Study 3, subjects in China and the United States reported probability distribution judgments for various quantities, e.g., the maximum temperature on a specified day. Judgment accuracy was evaluated overall and with respect to several underlying accuracy dimensions. The overall quality of discretealternative judgments was indistinguishable among the subjects from the three countries. The accuracy component patterns of the Japanese and American subjects were essentially the same. However, the Chinese subjects achieved the common overall accuracy level very differently. On some accuracy dimensions, e.g., calibration, the American and Japanese subjects' judgments were superior. On others, e.g., discrimination, the assessments of the Chinese subjects excelled. Results for quantity judgments were similar to those for disCrete alternative judgments, although there were notable differences. Potential explanations and implications are discussed. 8 1x39 Academic RCSS, I~C.

The "real time" formulation of time-dependent density functional theory (TDDFT) involves integration of the time-dependent Kohn-Sham (TDKS) equation in order to describe the time evolution of the electron density following a perturbation. This approach, which is complementary to the more traditional linear-response formulation of TDDFT, is more efficient for computation of broad-band spectra (including core-excited states) and for systems where the density of states is large. Integration of the TDKS equation is complicated by the time-dependent nature of the effective Hamiltonian, and we introduce several predictor/corrector algorithms to propagate the density matrix, one of which can be viewed as a self-consistent extension of the widely used modified-midpoint algorithm. The predictor/corrector algorithms facilitate larger time steps and are shown to be more efficient despite requiring more than one Fock build per time step, and furthermore can be used to detect a divergent simulation on-the-fly, which can then be halted or else the time step modified.

High harmonic spectra for H2 and [Formula: see text] are simulated by solving the time-dependent Kohn–Sham equation in the presence of a strong laser field using an atom-centered Gaussian representation of the density and a complex absorbing potential. The latter serves to mitigate artifacts associated with the finite extent of the basis functions, including spurious reflection of the outgoing electronic wave packet. Interference between the outgoing and reflected waves manifests as peak broadening in the spectrum as well as the appearance of spurious high-energy peaks after the harmonic progression has terminated. We demonstrate that well-resolved spectra can be obtained through the use of an atom-centered absorbing potential. As compared to grid-based algorithms, the present approach is more readily extensible to larger molecules.

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