  Earlier studies of grain alignment dealt mostly with interstellar grains that
have strong internal relaxation of energy which aligns grain axis of maximum
moment of inertia with respect to grain's angular momentum. In this paper, we
study the alignment by radiative torques for large irregular grains, e.g.,
grains in accretion disks, for which internal relaxation is subdominant. We use
both numerical calculations and the analytical model of a helical grain
introduced by us earlier. We demonstrate that grains in such a regime exhibit
more complex dynamics. In particular, if initially the grain axis of maximum
moment of inertia makes a small angle with angular momentum, then radiative
torques can align the grain axis of maximum moment of inertia with angular
momentum, and both axis of maximum moment of inertia and angular momentum are
aligned with the magnetic field when attractors with high angular momentum
(high-J attractors) are available. For the alignment without high-J attractors,
beside the earlier studied attractors with low angular momentum (low-J
attractors), there appears new low-J attractors. The former and later cases
correspond to the alignment with long axes perpendicular and parallel to the
angular momentum, respectively. In addition, we study the alignment of grains
in the presence of strong internal relaxation, but induced not by a radiation
beam as in earlier studies, instead, induced by a complex radiation field, that
can be decomposed into dipole and quadrupole components. We find that in this
situation, the parameter space $q^{max}$, for the existence of high-$J$
attractors is more extended, which entails higher degrees of polarization
expected. Our obtained results are useful for modeling polarization arising
from aligned grains in molecular clouds and accretion disks.
