  Recently, Tavarone et al. (J. Chem. Phys. 143, 114505 (2015)) discussed phase
behavior of zig-zag and bow-shaped particles composed of three needles. The
authors presented very interesting results of extensive Monte Carlo simulations
with periodic boundary conditions in the constant-NVT and the constant-NPT
ensembles. In addition to isotropic, nematic, and smectic phases, they
identified a modulated nematic, which is actually the nematic splay-bend phase
($N_{SB}$), long-anticipated for bent-core systems (Europhys. Lett. 56, 247
(2001)). They also described isotropic-nematic and nematic-smectic transitions
using Density Functional Theory in mean-field approximation. The authors,
however, did not provided a theoretical description of the $N_{SB}$. Here, we
present a simple theory of a phase transition to the $N_{SB}$ phase to fill the
gap. In our study, we use Onsager-type Density Functional Theory with perfect
order approximation and Meyer parametrization of modulated structures. We
present results for arbitrary ratios of the length of central and side segments
and opening angles of bow-shaped particles.
