  Based on neutron wide-angle diffraction and small-angle neutron scattering
experiments, we show that there is a correlation between the preparational
conditions of amorphous ice structures, their microscopic structural
properties, the extent of heterogeneities on a mesoscopic spatial scale and the
transformation kinetics. There are only two modifications that can be
identified as homogeneous disordered structures, namely the very high-density
vHDA and the low-density amorphous LDA ice. Structures showing an intermediate
static structure factor with respect to vHDA and LDA are heterogeneous phases.
This holds independently from their preparation procedure, i.e. either obtained
by pressure amorphisation of ice I_h or by heating of vHDA. The degree of
heterogeneity can be progressively suppressed when higher pressures and
temperatures are applied for the sample preparation. In accordance with the
suppressed heterogeneity the maximum of the static structure factor displays a
pronounced narrowing of the first strong peak, shifting towards higher
Q-numbers. Moreover, the less heterogeneous the obtained structures are the
slower is the transformation kinetics from the high--density modifications into
LDA. The well known high-density amorphous structure HDA does not constitute
any particular state of the amorphous water network. It is formed due to the
preparational procedure working in liquid nitrogen as thermal bath, i.e. at
about 77 K.
