Foundations of Crystallography

 

Acta Cryst. (2000). A56, 403-412  [ doi:10.1107/S0108767300005626 ]

Dynamics of molecules in crystals from multi-temperature anisotropic displacement parameters. I. Theory

H. B. Bürgi and S. C. Capelli

Synopsis: A mean-field model describing the temperature evolution of anisotropic displacement parameters (ADP's) is presented. With this model, ADP's pertaining to different temperatures may be analysed for mutual consistency, for correlations of atomic displacements as well as for contributions from disorder and systematic error.

Online September 2000

 

Acta Cryst. (2000). A56, 413-424  [ doi:10.1107/S0108767300005638 ]

Dynamics of molecules in crystals from multi-temperature anisotropic displacement parameters. II. Application to benzene (C₆D₆) and urea [OC(NH)₂]

S. C. Capelli, M. Förtsch and H. B. Bürgi

Synopsis: Anisotropic displacement parameters (ADP's) of C₆D₆ and OC(NH₂)₂ from neutron diffraction experiments in the temperature range 12-123  K are analysed with the mean-field model presented in the preceding paper. Some features of the molecular dynamics are derived from the multi-temperature ADP's and found to agree well with those from independent spectroscopic experiments.

Online September 2000

 

Acta Cryst. (2000). A56, 425-435  [ doi:10.1107/S0108767300008734 ]

Anharmonicity in anisotropic displacement parameters

H. B. Bürgi, S. C. Capelli and H. Birkedal

Synopsis: A model for the anharmonic temperature evolution of anisotropic displacement parameters is developed and tested with X-ray and neutron diffraction data from hexamethylenetetramine measured between 15 and 298  K.

Online September 2000

 

Acta Cryst. (2000). A56, 436-450  [ doi:10.1107/S0108767300006668 ]

Strategies for structure solution and refinement of small organic molecules from electron diffraction data and limitations of the simulation approach

R. C. Yu, A. V. Yakimansky, H. Kothe, I. G. Voigt-Martin, D. Schollmeyer, J. Jansen, H. Zandbergen and A. V. Tenkovtsev

Synopsis: It is shown that structure solution and refinement of non-linear optically active molecular crystals is possible based on electron diffraction combined with quantum mechanics, packing-energy calculations and direct methods.

Online September 2000

 

Acta Cryst. (2000). A56, 451-457  [ doi:10.1107/S0108767300006966 ]

SIR2000, a program for the automatic ab initio crystal structure solution of proteins

M. C. Burla, M. Camalli, B. Carrozzini, G. L. Cascarano, C. Giacovazzo, G. Polidori and R. Spagna

Synopsis: A new phasing procedure is described, able to solve the ab initio crystal structures of proteins with up to 2000 non-hydrogen atoms in the asymmetric unit.

Online September 2000

 

Acta Cryst. (2000). A56, 458-469  [ doi:10.1107/S0108767300007066 ]

Statistical dynamical direct methods. I. The effective kinematical approximation

J. J. Hu, F. N. Chukhovskii and L. D. Marks

Synopsis: It is shown that, even though the kinematical theory for electron diffraction is not rigorously accurate for transmission electron diffraction except for unrealistically thin samples, the statistical distribution of phases retains many kinematical characteristics.

Online September 2000

 

Acta Cryst. (2000). A56, 470-490  [ doi:10.1107/S0108767300007078 ]

Atomic scattering factors for K-shell and L-shell ionization by fast electrons

M. P. Oxley and L. J. Allen

Synopsis: Atomic scattering factors have been calculated for ionization by fast electrons from the K shell for elements in the range Z = 6 to 50 and from the L shell for Z = 20 to 60.

Online September 2000

 

Acta Cryst. (2000). A56, 491-496  [ doi:10.1107/S0108767300007145 ]

The contraction types of parallelohedra in E⁵

P. Engel

Synopsis: A general process to derive systematically the contraction types of parallelohedra is described. Then numbers of contraction types of parallelohedra in E⁵ are given for each of the 84 contraction families.

Online September 2000

 

Acta Cryst. (2000). A56, 497-506  [ doi:10.1107/S0108767300008138 ]

Diffraction by one-dimensional paracrystals and perturbed lattices

R. P. Millane and J. L. Eads

Synopsis: The paracrystalline and perturbed lattice models of disordered crystals, and their diffraction patterns, are compared in the one-dimensional case.

Online September 2000

 

Acta Cryst. (2000). A56, 507-508  [ doi:10.1107/S0108767300009077 ]

Bragg-surface dynamical diffraction

L. H. Avanci and S. L. Morelhão

Synopsis: The dynamical theory of X-ray diffraction is applied to Bragg-surface diffraction. A solution for the boundary condition of this unusual three-beam diffraction is presented.

Online September 2000

 

Acta Cryst. (2000). A56, 509  [ doi:10.1107/S0108767300007261 ]

Direct phasing in crystallography

Online September 2000

 

Acta Cryst. (2000). A56, 510  [ doi:10.1107/S0108767300008059 ]

Diffraction des rayonnements

Online September 2000