TABLE II: Density fitting errors in the two-electron repulsion integrals (δ DF ) and MP2 correlation energy (∆DF) for the anion of the Te atom. The VTZ-F12-MP2Fit ABS is augmented with a series of additional diffuse functions. In the case of even1f1g, the exponents of the additional functions are determined by even-tempered extension, rather than free optimization From Table it can be seen that adding an additional set of g functions to the ABS (denoted "VTZ-F12 + 1g") produces a significant reduction in the density fitting error metrics, including greater than an order of magnitude improvement in the accuracy of the DF-MP2 correlation energy. Perhaps more significantly, adding a combination of both f and g functions results in density fitting errors that are roughly on par with the baseline results observed for the VTZ-F12 OBS paired with the matching MP2Fit ABS. An alternative to freely optimizing the exponents of these f and g exponents is also explored, namely an even-tempered extension of the existing exponents. In this extension, the two most diffuse functions in a specific angular shell, ζ l 1 and ζ l 2 , are used to define the new diffuse exponent as