  The temperature-dependent Matsubara Green's function that is used to describe
temperature-dependent behavior is expressed on a numerical grid. While such a
grid usually has a couple of hundred points for low-energy model systems, for
realistic systems in large basis sets the size of an accurate grid can be tens
of thousands of points, constituting a severe computational and memory
bottleneck. In this paper, we determine efficient imaginary time grids for the
temperature-dependent Matsubara Green's function formalism that can be used for
calculations on realistic systems. We show that due to the use of orthogonal
polynomial transform, we can restrict the imaginary time grid to few hundred
points and reach micro-Hartree accuracy in the electronic energy evaluation.
Moreover, we show that only a limited number of orthogonal polynomial expansion
coefficients are necessary to preserve accuracy when working with a dual
representation of Green's function or self-energy and transforming between the
imaginary time and Matsubara frequency domain.
