We perform ab initio quantum Monte Carlo (QMC) simulations of the warm dense uniform electron
gas in the thermodynamic limit. By combining QMC data with linear response theory we are able to
remove finite-size errors from the potential energy over the entire warm dense regime, overcoming the
deficiencies of the existing finite-size corrections by Brown et al. [PRL 110, 146405 (2013)]. Extensive
new QMC results for up to N = 1000 electrons enable us to compute the potential energy V and the
exchange-correlation free energy Fxc of the macroscopic electron gas with an unprecedented accuracy
of |∆V |/|V |, |∆Fxc|/|F|xc ∼ 10−3
. A comparison of our new data to the recent parametrization of
Fxc by Karasiev et al. [PRL 112, 076403 (2014)] reveals significant deviations to the latter.