Abstract
AbstractThe crystal structures and formation reactions of lanthanum hydride selenides were studied by neutron diffraction on the deuterides. The reaction of La2D2−x Se with deuterium gas (298 K≤T≤567 K, 0.1 MPa≤p(D2)≤9.0 MPa) was followed in situ by neutron diffraction in a sapphire single‐crystal gas‐pressure cell with a time resolution of two minutes. The crystal structures and phase fractions of La2D2−xSe, La2D3Se and La2D4Se were determined by Rietveld refinement. With stepwise increasing deuterium pressure at 498 K up to 3.0 MPa La2D2−xSe is deuterated to La2D4Se. La2D3Se remains present, even when further increasing the pressure up to 9.0 MPa and heating up to 567 K. The previously suggested structural models were confirmed by Rietveld refinement (La2D1.6Se: Ce2O2S type, m1, a=4.1268(1) Å, c=6.8733(3) Å at 298 K; La2D3Se: Ba2H3Cl type, m1, a=4.139(2) Å, c=6.960(5) Å at 298 K; La2D4Se: Ce2F4Se type, m, a=4.0542(2) Å, c=22.609(2) Å at 310 K). La2D2−x Se exhibits a considerable hydrogen gas pressure dependent phase width (0≤x<0.40).
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