Max Ferdinand Perutz 1914–2002

Local squaring functions

A class of functions representing localized atomic form information is introduced and phase refinement and automated map interpretation aspects are investigated. A simple iterative phase refinement procedure based on atomic form constraints is applied to three small metalloproteins, with overall improvements of 20 to 40° in mean phase error and 0.2 in map correlation.

The asymptotic leading term of anisotropic small-angle scattering intensities. II. Non-convex particles

The anisotropic Porod law is extended to particulate samples where particles have non-convex shapes with possible planar facets.

Wavefunctions derived from experiment. III. Topological analysis of crystal fragments

A new constrained wavefunction model that utilizes experimental X-ray structure factors has been used to produce a charge density distribution for crystalline α-oxalic acid dihydrate. Topological and integrated atomic properties have been derived from this electron density, including estimates of the experimental errors associated with these quantities, and the influence of both the basis sets and the choice of experimental data on these properties has been examined.

Wavefunctions derived from experiment. IV. Investigation of the crystal environment of ammonia

The constrained wavefunction procedure has been applied to experimental data for NH₃. Different molecular environments have been used to construct the theoretical crystal and integrated atomic properties have been derived. The accuracy of these properties and the error in the experimental σ(k) values has been estimated.

Three-beam X-ray diffraction in a semi-infinite perfect crystal

The analytical theory for three-beam diffraction based on a Born series for the displacement field in a semi-infinite crystal is reexamined. Results are obtained in agreement with the Takagi–Taupin formalism.

Energy landscape paving for X-ray structure determination of organic molecules

A new optimization approach, energy landscape paving, is employed for finding the crystal structure of organic molecules. The efficiency of this method is compared with simulated annealing.

Ab initio determination of a crystal structure by means of the Schrödinger equation

The Schrödinger equation as the basis of a novel solution of the phase problem. Theoretical developments.

Likelihood-based refinement. I. Irremovable model errors

Motivations to use likelihood-based residuals are discussed. The quadratic approximation of the likelihood function enables one to consider the likelihood-based refinement as a kind of conventional least-squares refinement and to study the differences between these criteria.

Direct phasing by binary integer programming

The phase problem may be reduced to the solution of a system of linear inequalities in binary unknowns. Integer programming can be used for low-resolution ab initio phasing.

Diffraction by partially occupied helices

An expression for cylindrically averaged intensity diffracted by a partially occupied helix (i.e. by a set of identical molecules bound to some points of a discrete helix) is derived. The result is compared with previous studies and its application to muscle diffraction is discussed.

On the spectrum of fullerenes

The most symmetrical C₅₀ to C₇₀ fullerenes with minimum numbers of pairs of adjacent pentagonal facets are considered in this paper.

Normal-mode analysis of the structures of perovskites with tilted octahedra. Erratum

Erratum to Acta Cryst. (2002). A58, 66–71.

Corrections to Crystallographic Groups of Four-Dimensional Space by Brown et al. (1978) [New York: Wiley and Sons]

An error is corrected in the tabulation of enantiomorphic space-group types given in the book Crystallographic Groups of Four-Dimensional Space by Brown et al. (1978).

Ewald Prize awarded to Professor Michael Woolfson

Physics meets mineralogy: condensed matter physics in the geosciences.

Applications of neutron scattering to soft condensed matter.