In a previous study (Stahl and Bredow, Chem. Phys. Lett. 2018, 695, 28–33), we have studied structural, energetic, and electronic properties of two vanadium dioxide VO2 polymorphs with modified global and range‐separated hybrid functionals. Since hybrid methods are computationally demanding, we evaluate the computationally more efficient DFT + U method in the present study. We assessed the widely used Dudarev PBE + U approach with a literature value of the effective Hubbard parameter Ueff = 3.4 eV. We compared the PBE + U results for the two VO2 polymorphs with our previous results, a self‐consistent hybrid functional sc‐PBE0, and the meta‐GGA functional SCAN. It was found that the PBE + U method yields a strongly distorted monoclinic phase and does not reproduce the metal‐to‐insulator transition of VO2 correctly, even with modified values of Ueff. On the other hand, sc‐PBE0 and SCAN describe the relative stability and the electronic structure of both polymorphs correctly and also provide reasonable lattice parameters. The functional SCAN yields the optimal balance between computational efficiency and accuracy. © 2019 The Authors. Journal of Computational Chemistry published by Wiley Periodicals, Inc.

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Vanadium dioxide is an interesting and frequently applied material due to its metal‐insulator phase transition. However, there are only few studies of the catalytic activity and surface properties of different VO2 polymorphs. Therefore, we investigated the properties of the surfaces of the most stable VO2 phases theoretically at density‐functional theory level using a self‐consistent hybrid functional which has demonstrated its accuracy for the prediction of structural, electronic and energetic properties in a previous study. We found that the surfaces of the rutile R phase of VO2 are not stable and show a spontaneous phase transition to the monoclinic M1 phase. Doping with Mo stabilizes the surfaces with rutile structure even for small dopant concentrations (6.25 %). Both M1 and R surfaces strongly relax, with and without doping. In particular the metal‐metal distances in the uppermost layers change by up to 0.4 Å. Mo segregates in the topmost layer of both R and M1 phases. The electronic structure is only slightly changed upon doping.

VO 2 is well known for its low-temperature metal-insulator transition between two phases with tetragonal rutile and monoclinic structure. The adsorption of CO on the two polymorphs of Mo-doped VO 2 is calculated to investigate the effect of a substrate phase change on the adsorption energy. The system is investigated theoretically at density-functional theory level using a hybrid functional with London dispersion correction. We establish a computational protocol applicable for the study of physisorption on open-shell transition metal oxides. The main task is to control the spin state of open-shell slab models used to model adsorption of closed-shell molecules in order to obtain numerically stable adsorption energies and to reduce spin contamination within the broken-symmetry unrestricted Kohn-Sham approximation. Applying this procedure, it is possible to identify the most stable adsorption positions of CO on both phases of VO 2 . CO adsorbs vertically with the C atom on a surface V atom in the monoclinic phase with an adsorption energy of À 56 kJ/mol. The same adsorption position has an adsorption energy of only À 46 kJ/mol on the rutile phase. Similar differences were obtained with multireference methods using an embedded cluster model. This effect may inspire experimental strategies exploiting the rutile$monoclinic VO 2 phase transition in catalytic processes where CO is formed as product or as an intermediate.