  When the system with internal tendency to a spontaneous formation of a
spatially periodic state is brought in contact with the external explicit
periodic potential, the interesting phenomenon of commensurate lock in can be
observed. In case when the explicit potential is strong enough and its period
is close to the period of the spontaneous structure, the latter is forced to
assume the periodicity of the former and the commensurate state becomes a
thermodynamically preferred one. If instead the two periods are significantly
different, the incommensurate state is formed. It is characterized by a finite
density of solitonic objects -- discommensurations -- on top of the
commensurate state. In this note I study the properties of discommensurations
in holographic model with inhomogeneous translational symmetry breaking and
explain how one can understand the commensurate/incommensurate phase transition
as a proliferation of these solitons. Some useful numerical techniques are
discussed in the Appendix.
