Applying connectivity twist averaging to quantum Monte Carlo and real solids*

In wavefunction-based periodic solid calculations, converging calculations to the thermodynamic limit (TDL) is important due to the finite size effects. Many methods, such as additive corrections and twist averaging, have been developed to combat this error that is difficult to remove. These improve the overall accuracy of many quantum Monte Carlo methods. However, twist averaging can have higher costs as a calculation needs to be run at each twist angle. We developed a method for the uniform electron gas (UEG) we termed connectivity twist averaging (cTA) that helps combat this increased cost. In this method, we select a single twist angle that represents the twist averaging system and run a single wavefunction-based calculation, obtaining twist averaged results at a fraction of the cost. As we have only demonstrated the application of this method to the UEG using coupled cluster, here, I will show how this method can be applied to quantum Monte Carlo methods, using full configuration interaction quantum Monte Carlo, as well as applications to real systems using a modified version of the cTA method.