International Tables for Crystallography

Phase improvement by iterative density modification
K. Y. J. Zhang, K. D. Cowtan and P. Main. International Tables for Crystallography (2012). Vol. F, ch. 15.1, pp. 385-400  [ doi:10.1107/97809553602060000847 ]


Density modification is a method for improving phase estimates arising from sources such as MIR/MAD and molecular replacement. This is achieved by use of chemical knowledge concerning the properties of well phased electron-density maps, including such features as solvent flatness, atomic composition and noncrystallographic symmetry. The calculation is performed iteratively, with alternating stages of map modification in real space and phase weighting in reciprocal space.

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International Tables for Crystallography is the definitive resource and reference work for crystallography. The series consists of nine volumes and comprises articles and tables of data relevant to crystallographic research and to applications of crystallographic methods in all sciences concerned with the structure and properties of materials.