Abstract: Materials design in a variety of industries would be helped by the development of new ab initio quantum chemistry methods to model electron-electron interactions in solids. Progress in this area is challenging because of electron correlation and specialized techniques that show potential are coupled cluster theory and quantum Monte Carlo. I will discuss ways in which we are trying to address two barriers preventing the widespread adoption of these methods. In the first part of my talk, I will show how we used coupled cluster theory to calculate the transition pressure of silicon. To achieve this, we had to design new methods to overcome finite size effects which come from having relatively few atoms in our simulation cell. In the second part of my talk, I will describe our efforts to simulate how electronic structure behaves under extremely high temperatures. I will show our improvements of a quantum Monte Carlo technique that models the full quantum mechanical density matrix for interacting electrons. I will show example applications on atomic ionization and bond breaking.