ChemBrain's similarity-search option enables you to find molecules that are similar to a particular molecule. For this purpose, you first select this molecule from the structure database, the data of which are then shown in its datasheet. 

Yet, an important question is: similar to which property of the molecule in question? ChemBrain provides several options: the distribution in the molecule of either the atomic masses, charges, polarizabilities, electronegativities or VdW volumes. Beyond this, you can choose between three auto-correlation types: the radial-distribution function (RDF), the topology or the surface (the latter being restricted to the distribution of the molecular electrostatic potential on the VdW surface).

Once you have selected one of these options, you start the similarity seach by clicking the button below the structure representation code (see screenshots). Optionally, you can restrict the similarity search by a class and/or a single-value property from a given list and by a minimum similarity constraint.

The result of the similarity search is given as a hitlist, which is sorted by decreasing similarity and limited to a maximum of 25 hits. Doubleclicking on any of the hit molecules immediately opens the corresponding molecule datasheet.

A simple example is shown in the screenshots.