Two aspects of chemical systems may be used to reduce the cost of electronic structure computations. Linear scaling takes advantage of nearsightedness, whereby interactions become less complex with increasing distance. Here, we take advantage of molecular similarity, whereby molecular fragments behave similarly in similar environments.  The approach begins by generating a large set of ab initio data for a set of molecules in a range of geometries and electrostatic environments.  Parameters are then embedded in a low-level ab initio method and adjusted to reproduce the results of a high-level method. In addition to total energy, agreement is sought for individual operators. The parameters modify the operator matrix elements and depend on both atom type and state (e.g. charge or coordination number). The use of this approach to get a small basis set calculation to agree with a large basis set calculation over a restricted class of molecules will be presented.

Using molecular similarity to reduce the cost of electronic structure calculations

244th National Meeting (2012)

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