Molecular electron density Lego approach to molecule building

A new method is presented for the construction of ab initio quality approximate electronic charge distributions for large molecules from charge distributions of small molecular fragments. This method is reminiscent to building structures using Lego blocks. The electronic density distribution calculated using the method is quantitatively shown to be very similar to that calculated for entire molecules using conventional ab initio packages with standard basis sets such as 6-31G ** , while requiring only a fraction of the computational time. The pre-calculated fuzzy electron distributions of base molecular fragments, stored in a data bank, are merged (rotated, translated, and subsequently added together) to calculate these approximate charge distributions for the molecule