Removal of the bottleneck in local correlation methods

We present preliminary results from a new hybrid pseudospectral local correlation method in which we combine the pseudospectral approximation to two-electron integral evaluation with local truncation of the virtual space to accelerate singles and double excitation configuration interaction (SDCI). The combination of the two leads even in small molecules to overall speed-ups of factors of 3–5 and reduces the main disk space requirement by factors of 9–20 while retaining at least 98% of the correlation energy of the exact SDCI calculations. These preliminary results bode well for the advantages of further development of pseudospectral local correlation methods.