Evolutionary Algorithm‐Based Crystal Structure Prediction for Copper(I) Fluoride

Abstract

Despite numerous experimental studies since 1824, the binary copper(I) fluoride remains unknown. A crystal structure prediction has been carried out for CuF using the USPEX evolutionary algorithm and a dispersion‐corrected hybrid density functional method. In total about 5000 hypothetical structures were investigated. The energetics of the predicted structures were also counter‐checked with local second‐order Møller–Plesset perturbation theory. Herein 39 new hypothetical copper(I) fluoride structures are reported that are lower in energy compared to the previously predicted cinnabar‐type structure. Cuprophilic Cu−Cu interactions are present in all the low‐energy structures, leading to ordered Cu substructures such as helical or zig‐zag‐type Cu−Cu motifs. The lowest‐energy structure adopts a trigonal crystal structure with space group P3121. From an electronic point of view, the predicted CuF modification is a semiconductor with an indirect band gap of 2.3 eV.

Evolutionary Algorithm‐based Crystal Structure Prediction for Gold(I) Fluoride

“…Composition produced the highest‐symmetry crystal structures of our USPEX simulations. They all adopt trigonal crystal structures reminescent of the topology of the cinnabar structure type previously predicted for CuF . The lowest‐energy structure B adopts the space group (Figure ).…”

“…The hybrid DFT‐PBE0 functional has been shown to produce consistent structures and energetics for a number of d ‐metal fluorides . We have recently used the DFT‐PBE0‐D3 approach to investigate hypothetical copper(I) fluorides and in addition to describing the cuprophilic interactions, the method also properly described the experimentally known group 11 fluorides CuF 2 and AgF . The basis sets used were Gaussian‐type triple‐ ζ ‐valence+polarization (TZVP) and split‐valence+polarization (SVP) derived from molecular Karlsruhe def2 basis sets …”

“…Formula units were investigated from to , and except for the computationally more demanding and , two USPEX simulations were carried out. Composition was judged to be too small already in our previous study for CuF . Composition was found to produce the lowest energy structure, and thus two further USPEX simulations were carried out with using an external hydrostatic pressure of 20 GPa in the CRYSTAL geometry optimizations.…”

“…The use of structure prediction algorithms enables the evaluation of potential structures which may adopt an unexpected or unique structure type . Evolutionary algorithms have so far been used successfully in many structural prediction studies of transition metal compounds and prospective materials based on them, both at ambient and higher pressures . The valence states of gold in Au−F compounds under high pressure have very recently been studied by Liu et al .…”

“…We describe an evolutionary algorithm‐based crystal structure prediction study for gold(I) fluoride using the USPEX (Universal Structure Predictor: Evolutionary Xtallography) algorithm and dispersion‐corrected hybrid density functional methods. We have recently used the same methodology for investigating copper(I) fluoride, resulting in several novel structural candidates that possess lower energy than the previously reported hypothetical CuF crystal structures . We also investigate the known binary gold fluorides AuF 3 , AuF 5 , and Au 3 F 8 and the previously reported hypothetical AuF crystal structures at the same level of theory.…”