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.

Due to the severe self-interaction errors associated with some density functional approximations, conventional density functionals often fail to dissociate the hemibonded structure of water dimer radical cation (H2O)2 + into the correct fragments: H2O and H2O + . Consequently, the binding energy of the hemibonded structure (H2O)2 + is not well-defined. For a comprehensive comparison of different functionals for this system, we propose three criteria: (i) The binding energies, (ii) the relative energies between the conformers of the water dimer radical cation, and (iii) the dissociation curves predicted by different functionals. The long-range corrected (LC) double-hybrid functional, ωB97X-2(LP) [J.-D. Chai and M. Head-Gordon, J. Chem. Phys., 2009, 131, 174105.], is shown to perform reasonably well based on these three criteria. Reasons that LC hybrid functionals generally work better than conventional density functionals for hemibonded systems are also explained in this work.

Dinoflagellates in the genus Hematodinium are important parasites of wild marine crustaceans, but are rarely reported in waters with salinities <11 or from cultured crustaceans. Since 2005, the mud crab Scylla serrata, which is cultured along the coast of southeastern China, has suffered from an acute epizootic locally known as 'milky disease'. The disease mainly occurrs from September to November. The clinical signs are largely similar to those of crabs suffering from bitter crab disease (BCD) or pink crab disease (PCD), which are caused by parasites of the genus Hematodinium. To determine whether Hematodinium sp. is a pathogen of milky disease, histopathological examinations of mud crab haemolymph, hepatopancreas, heart and gill were conducted. In addition, previously reported Hematodinium molecular probes were applied to infected material. The results indicate that Hematodinium sp. is at least one of the main pathogens of milky disease. The salinity in S. serrata culture ponds was < 9. To our knowledge, this is the first report showing the Hematodinium infection in a cultured crustacean in low salinity water.

Abstract.Using density functional theory with empirical van der Waals corrections, cold pressure curves were calculated and combined with the quasi-harmonic approximation to study thermodynamical properties of several energetic molecular solids. Vibration spectra at each compression were calculated and used for including temperature and zero-point energy contributions to the free energy. Equilibrium properties at temperatures of experiments, as well as hydrostatic equations of state, specific heat capacities, and coefficients of thermal expansion, were obtained and compared to experiment.

The longan lanternfly Pyrops candelaria is a new invasive species on the main island of Taiwan. The introduction of an invasive species may negatively influence the native fauna, flora and environment. Thus, this study aimed to infer the invasion history, predict habitat suitability and potential expansion and assess the risk to crop cultivation areas in Taiwan. Genetic structures of P. candelaria from the main island of Taiwan and related regions were analyzed based on partial COI and ND2 sequences. Additionally, machine learning MaxEnt was utilized to study habitat suitability. The results suggested that the Taiwanese populations may originate from the Kinmen Islands and the plain areas of Taiwan are considered to have high habitat suitability. Furthermore, most of the cultivation areas of longan and pomelo crops showed high habitat suitability.