Neutron-diffraction refinement of atomic structure of α- and γ-phases of crystals of Li3Sc2(PO4)3 at 293 and 573 K

At 293 and 573 K from neutron-diffraction data the authors have refined the atomic structures of the α- and γ-phases of Li 3 Sc 2 (PO 4 ) 3 crystals. At room temperature the investigated crystal in the α-phase is twinned according to a merohedral law with twinning index n=1. The parameters of the monoclinic unit cell are a=8.848(3), b=12.270(4), c=8.801(2) A, γ=90.02(2)°, space group P2 1 /n. Refinement was effected with allowance for twinning over 2460 independent reflections with I nkl >3σ I ; R=4.4%, R W =3.7%. At 573 K after completion of the phase transition to the orthorhombic symmetry group C 2h 5 ⇄D 2h '14 the crystal becomes monodomain : space group Pcan, a=8.829(3), b=12.397(3), c=8.821(2) A. In this case the structural parameters were refined from 492 independent reflections with I nkl >3σ I ; R=3.6%, R W =3.8%. The neutron-diffraction data are compared with previously obtained x-ray structural data