Second order Moller-Plesset theory (MP2) in small basis sets is known to perform poorly for inter- and intra-molecular interactions due primarily to the effect of basis set superposition error (BSSE) and secondarily to intrinsic accuracy limitations for some classes of interactions such as pi stacking.  In the relatively small aug-cc-pVDZ basis, we demonstrate that remarkable improvements in accuracy are possible (three to five-fold reductions in RMS errors) by attenuating the MP2 correlation contribution as a function of inter-electronic distance.  These improvements result primarily from being able to eliminate BSSE effects by attenuation.  Equally remarkably, the small basis attenuated MP2 results are even statistically superior to complete basis set limit MP2 calculations for a range of intra- and inter-molecular interactions, despite being many hundreds of times cheaper.  This small basis attenuated MP2 method should be valuable for intra- and inter-molecular interactions that are too large for higher cost approaches.

Attenuating away the errors in inter and intra-molecular interactions from second order Moller-Plesset calculations in small basis sets

245th National Meeting (2013)

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