ShakePSD: automatic phase solver covering heavy-atom methods and direct methods for Windows PCs

A new computer program, ShakePSD (filtering using the Patterson function, search procedures and direct methods), has been developed to solve the structures of organic compounds automatically on personal computers (PCs) operating under Windows. ShakePSD is a single program that can discriminate whether a heavy-atom is included or not and can employ heavy-atom methods (Patterson function and search for all remaining atoms) or direct methods (tangent formula and/or minimal function). A new subroutine, MINIMAL, adopts the Karle recycling method based on the minimal-function theory. The input data are cell constants, space group, number of atoms with atomic types and observed structure factors F_o(h). Compared to the TANGENT procedure (employing the tangent formula), MINIMAL is able to obtain the same or a larger number of atoms in a run set and the number of run sets is distinctly larger in a single computer execution. MINIMAL is a powerful procedure, but it takes a considerable amount of processing time on a Windows PC. The output is in the form of two-dimensional projection diagrams of the molecules in a unit cell. ShakePSD is an automatic general phase solver, being able to handle both heavy-atom methods and direct methods within a single program, and determines, with certainty, molecular fragments.