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The evolution of scalar linear perturbations is studied in gauge-invariantapproach for 2-component models with nonrelativistic matter and minimallycoupled scalar fields, the potentials of which were constructed for eitherconstant dark energy equation of state (EoS) parameter $w$ or its adiabaticsound speed $c_a^2$ equal to zero. The numerical solutions show that suchfields are almost smoothed out on subhorizon scales. However they cause thescale dependent suppression of the nonrelativistic mater density perturbationsand the decay of gravitational potential, which can be used for choice of thedark energy model. We discuss 2 types of the Lagrangian: classical andtachyonic ones. As our results show, the fields with $w=const$ are almostindistinguishable, while for fields with $c_a^2=0$ the difference of darkenergy effective sound speeds $c_s^2$, which is caused by the shape ofLagrangian, affects the evolution of perturbations significantly. We presentalso the transfer functions for both components.

Perturbed dark energy: classical scalar field versus tachyon