  What kind of one-dimensional modulated nematic structures (ODMNS) can form
nonchiral and chiral bent-core and dimeric materials? Here, using
Landau-deGennes theory of nematics, extended to account for molecular steric
polarization, we study a possibility of formation of ODMNS, both in nonchiral
and intrinsically chiral liquid crystalline materials. Besides nematic and
cholesteric phases, we find four bulk ODMNS for nonchiral materials, two of
which have not been reported so far. These new structures are longitudinal
($N_{LP}$) and transverse ($N_{TP}$) periodic waves where the polarization
field being periodic in one dimension stays parallel and perpendicular,
respectively, to the wave vector. The other two phases have all characteristic
features of the twist-bend nematic phase ($N_{TB}$) and the splay-bend nematic
phase ($N_{SB}$), but their fine structure appears more complex than that
considered so far. The presence of molecular chirality converts nonchiral
$N_{TP}$ and $N_{SB}$ into new $N_{TB}$ phases. Interestingly, the nonchiral
$N_{LP}$ phase can stay stable even in the presence of intrinsic molecular
chirality. Exemplary phase diagrams provide further insights into the relative
stability of these new modulated nematic structures.
