  Extended solids are frequently simulated as finite systems with periodic
boundary conditions, which due to the long-range nature of the Coulomb
interaction may lead to slowly decaying finite- size errors. In the case of
Quantum-Monte-Carlo simulations, which are based on real space, both real-space
and momentum-space solutions to this problem exist. Here, we describe a hybrid
method which using real-space data models the spherically averaged structure
factor in momentum space. We show that (i) by integration our hybrid method
exactly maps onto the real-space model periodic Coulomb-interaction (MPC)
method and (ii) therefore our method combines the best of both worlds
(real-space and momentum-space). One can use known momentum-resolved behavior
to improve convergence where MPC fails (e.g., at surface-like systems). In
contrast to pure momentum-space methods, our method only deals with a simple
single-valued function and, hence, better lends itself to interpolation with
exact small-momentum data as no directional information is needed. By virtue of
integration, the resulting finite-size corrections can be written as an
addition to MPC.
