  The position operator in a Bloch representation acquires a gauge correction
in the momentum space on top of the canonical position, which is called the
anomalous position. We show that the anomalous position is generally
orbital-dependent and thus plays a crucial role in the description of the
intrinsic orbital Hall effect in terms of Wannier basis. We demonstrate this
from the first-principles calculation of orbital Hall conductivities of
transition metals by Wannier interpolation. Our results show that consistent
treatment of the velocity operator by adding the additional term originating
from the anomalous position predicts the orbital Hall conductivities different
from those obtained by considering only the group velocity. We find the
difference is crucial in several metals. For example, we predict the negative
sign of the orbital Hall conductivities for elements in the groups X and XI
such as Cu, Ag, Au, and Pd, for which the previous studies predicted the
positive sign. Our work suggests the importance of consistently describing the
spatial dependence of basis functions by first-principles methods as it is
fundamentally missing in the tight-binding approximation.
