Crystallography and mineralogy of nickel carbonate

The crystal structure of NiC03(cr) was definitively determined by Isaacs [63ISA]. It is of the calcite type, hexagonal, space group R3 c, Z = 6, with unit cell dimensions 3q = 4.609 A, Co = 14.737 A (according to JCPDS-ICDD card No. 12-771). 

The crystal structure of otwayite was investigated by Nickel et al. [77N1C/ROB]. Its fibre-rotation and X-ray powder diffraction patterns can be indexed on an orthorhombic unit cell with a = 10.18 A, b = 27.4 A, c = 3.22 A, Fceii = 898.16 A, Z = 8, /Xobs.) = 3.41 and p(calc.) = 3.346 g em (according to JCPDS-ICDD card No. 29-868). 

No synthesis of otwayite has been reported and no thermodynamic data have been determined so far. 

Isaacs studied the structure of zaratite [63ISA], The cell dimensions are a = 6.16 A, Z = 1 ceii = 233.74 p(calc.) = 2.31 g-cm , crystal system isometric, space group unknown (in part amorphous). 

A high temperature heat capacity function claimed to be valid at 298 (T/K) 700 for NiC03(cr) is given in thermodynamic data compilations  

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