BH3 under pressure : leaving the molecular diborane motif

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Journal titleJournal of the American Chemistry Society
Pages2100221009; # of pages: 8
AbstractMolecular and crystalline structures of (BH₃)n have been theoretically studied in the pressure regime from 1 atm to 100 GPa. At lower pressures, crystals of the familiar molecular dimer are the structure of choice. At 1 atm, in addition to the well-characterized β diborane structure, we suggest a new polymorph of B₂H₆, fitting the diffraction lines observed in the very first X-ray diffraction investigation of solid diborane, that of Mark and Pohland in 1925. We also find a number of metastable structures for oligomers of BH3, including cyclic trimers, tetramers, and hexamers. While the higher oligomers as well as one-dimensional infinite chains (bent at the bridging hydrogens) are less stable than the dimer at ambient pressure, they are stabilized, for reasons of molecular compactness, by application of external pressure. Using periodic DFT calculations, we predict that near 4 GPa a molecular crystal constructed from discrete trimers replaces the β diborane structure as the most stable phase and remains as such until 36 GPa. At higher pressures, a crystal of polymeric, one-dimensional chains is preferred, until at least 100 GPa.
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AffiliationNRC Steacie Institute for Molecular Sciences; National Research Council Canada
Peer reviewedYes
NPARC number19709140
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Record identifier7dfb0748-4d0f-487b-a0fe-4e7df7ce6415
Record created2012-03-28
Record modified2016-05-09
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