An analytic ring closure condition for geometrical algorithm to search the conformational space

The recently reported geometrical algorithm to search the conformational space (GASCOS) scans conformational space exhaustively using an internal coordinate tree search. Using only geometrical operations and a set of criteria for eliminating chemically unreasonable atomic arrangements, the algorithm generates starting geometries for optimizations by molecular mechanics or by molecular orbital procedures. Up until now GASCOS has been used for linear structures, but an extension to cyclic structures is reported here.