Multi-determinant Diffusion Monte Carlo in solids at the thermodynamic limit

In the past decade, fixed-node diffusion Monte Carlo using a single determinant Slater-Jastrow trial wavefunction as proven to systematically reproduce (within 5-10Kcal/mol) the energies of a wide range of molecules and solids. While it has been demonstrated for molecular systems that the path to chemical accuracy (<1Kcal/mol) can be realized by improving the nodal surface using for example multidetermiant trial wavefunctions generated with MCSCF or Selected CI. Reaching the same level of accuracy for solids in the thermodynamic limit has proven harder due to the exponential scaling of these wavefunction generation methods. In this talk, we will discuss the effect of using a multi-determinant Slater-Jastrow trial wavefunction with complex k-points and twist averaging in combination to reach chemical accuracy in the thermodynamic limit for solid carbon.