Crystal structure of the commensurately modulated ζ phase of PAMC

The commensurately modulated zeta low-temperature phase of bis(propylammonium) tetrachloromanganate(II), [NH3(C3H7)]2MnCl4, has been determined at 8 K. a = 7.437 (5), b = 7.082 (5), c = 13.096 (8) Angstrom, alpha = 105.59 (1)degrees. Superspace group P2(1)/b(0 beta 0)(1) over bar s, with beta = 1/3, V = 664.4, Z = 2 D-x = 1.58 g cm(-3) Mo K alpha radiation, lambda = 0.71069 Angstrom, mu = 17.99 cm(-1) F(000) = 326, wR(F) = 0.064 for 1444 main reflections and wR(F) = 0.089 for 248 satellite reflections. The modulation vector flips and locks into a commensurate value compared with the epsilon phase, indicating a 'lock-in' and phase shift between adjacent modulated layers. The modulation waves do not change much from the values of the epsilon phase, which confirms the lock-in of the modulation vector; only some components of the modulations of the propylammonium chains appear to be significantly different, these chains appear to be responsible for the phase shift across the layers.