TY  - JOUR
ID  - discovery1458752
UR  - http://dx.doi.org/10.1107/S205252061402126X
EP  -  962
N2  - We have determined the crystal structure of ammonium carbonate monohydrate, (NH4)2CO3·H2O, using Laue single-crystal diffraction methods with pulsed neutron radiation. The crystal is orthorhombic, space group Pnma (Z = 4), with unit-cell dimensions a = 12.047?(3), b = 4.453?(1), c = 11.023?(3)?Å and V = 591.3?(3)?Å(3) [?calc = 1281.8?(7)?kg?m(-3)] at 10?K. The single-crystal data collected at 10 and 100?K are complemented by X-ray powder diffraction data measured from 245 to 273?K, Raman spectra measured from 80 to 263?K and an athermal zero-pressure calculation of the electronic structure and phonon spectrum carried out using density functional theory (DFT). We find no evidence of a phase transition between 10 and 273?K; above 273?K, however, the title compound transforms first to ammonium sesquicarbonate monohydrate and subsequently to ammonium bicarbonate. The crystallographic and spectroscopic data and the calculations reveal a quite strongly hydrogen-bonded structure (EHB ? 30-40?kJ?mol(-1)), on the basis of H...O bond lengths and the topology of the electron density at the bond critical points, in which there is no free rotation of the ammonium cation at any temperature. The barrier to free rotation of the ammonium ions is estimated from the observed librational frequency to be ??36?kJ?mol(-1). The c-axis exhibits negative thermal expansion, but the thermal expansion behaviour of the a and b axes is ormal.
IS  - Pt 6
AV  - public
Y1  - 2014/12//
TI  - Structure, hydrogen bonding and thermal expansion of ammonium carbonate monohydrate.
JF  - Acta Crystallogr B Struct Sci Cryst Eng Mater
A1  - Fortes, AD
A1  - Wood, IG
A1  - Alfè, D
A1  - Hernández, ER
A1  - Gutmann, MJ
A1  - Sparkes, HA
KW  - Raman spectroscopy
KW  -  ammonium carbonate
KW  -  density functional theory
KW  -  neutron diffraction
SP  - 948 
VL  - 70
N1  - This is an open-access article distributed under the terms of the Creative Commons Attribution Licence, which permits unrestricted use, distribution, and reproduction in any medium, provided the original authors and source are cited.
ER  -