Oxalic acid dihydrate - an accurate low-temperature structural study using high-resolution neutron powder diffraction

Abstract

Deuterated oxalic acid dihydrate, C 2 D 4 .2D 2 O, M r =132.10, monoclinic, P2 1 /n, Z=2. At 100 K, a=6.13338 (6), b=3.50018 (1), c=11.98334 (3) A, β= 106.0599 (2) o , V=247.218 A 3 , D x =1.694 g cm -3 , χ 2 =1.93. At 15 K, a=6.13661 (4), b=3.47501 (1), c=11.97044 (2) A, β=105.9778 (1) o , V=245.406 A 3 , D x =1.706 g cm -3 , χ 2 =2.59. High-resolution neutron powder diffraction data have been recorded at temperatures of 15 and 100 K on fully deuterated oxalic acid dihydrate, which has been widely used as a crystallographic standard, in order to assess in particular the potential use of neutron powder diffraction data for charge-density studies