A model is proposed for the sliding charge density wave mechanism in the is
ostructural quasi-one-dimensional compounds NbSe3 and m-TaS3. It is based o
n an assumption that below either of the two onset temperatures T-1 and T-2
both modulation modes are present and form small statistically distributed
domains along particular trigonal prismatic columns, i.e., along type III
below T-1 and in addition along type I below T-2. Presuming the domains are
of comparable sizes to the coherence lengths in the diffraction experiment
s, their disordered distribution results in a selective contribution to the
reciprocal space in both temperature regions, which is in good accord with
the diffraction experiments. The model might form the basis for a better e
xplanation of the twinkling domains and low temperature tunneling microscop
ic images, which were not fully understood on basis of the old model with a
selective occupation of the two column types by the two modulation modes.