Foundations of Crystallography

 

Acta Cryst. (2000). A56, 105-111  [ doi:10.1107/S0108767399013355 ]

Upgrading the twin variables algorithm for large structures

K. Bethanis, P. Tzamalis, A. Hountas, A. F. Mishnev and G. Tsoucaris

Synopsis: Phase extension in protein molecules is presented. `Super-resolution' extension and a new figure of merit based on crystallographic symmetry are discussed.

Online March 2000

 

Acta Cryst. (2000). A56, 112-118  [ doi:10.1107/S0108767399014786 ]

Ill-conditioned Shake-and-Bake: the trap of the false minimum

H. Xu, C. M. Weeks, A. M. Deacon, R. Miller and H. A. Hauptman

Synopsis: False minima occurred frequently during Shake-and-Bake applications to large P1 data sets. These minima can be recognized and avoided with proper choice of parameter-shift conditions.

Online March 2000

 

Acta Cryst. (2000). A56, 119-126  [ doi:10.1107/S0108767399014798 ]

Inversion of dynamical electron diffraction data including absorption

L. J. Allen, H. M. L. Faulkner and H. Leeb

Synopsis: A method to obtain the crystal potential from the scattering matrix in dynamical electron diffraction, which takes absorption into account, is proposed.

Online March 2000

 

Acta Cryst. (2000). A56, 127-131  [ doi:10.1107/S0108767399014646 ]

Solving the Sayre equation by simulated annealing

Y. Chen and W.-P. Su

Synopsis: Simulated annealing can be used to solve the Sayre equation for ab initio structure determination. Trial calculations involving as many as 126 light atoms in the asymmetric unit are presented.

Online March 2000

 

Acta Cryst. (2000). A56, 132-148  [ doi:10.1107/S0108767399014907 ]

Twins and allotwins of basic mica polytypes: theoretical derivation and identification in the reciprocal space

M. Nespolo, G. Ferraris and H. Takeda

Synopsis: Geometrical criteria to identify the twins and allotwins of the four basic polytypes of mica from their diffraction patterns are derived and expressed by means of the `minimal rhombus' unit in reciprocal space.

Online March 2000

 

Acta Cryst. (2000). A56, 149-156  [ doi:10.1107/S0108767399014889 ]

New aspects in the crystal chemistry of (M₂Cu₂O₃)_m(CuO₂)_n-type (M = Ca, Sr, Y, Bi) cuprates

L. Leonyuk, G.-J. Babonas, V. Chernyshov, V. Rybakov, V. Maltsev and M. Baran

Synopsis: The phase (M₂Cu₂O₃)(Cu₁₊O₂₊) described as the member m/n = 1/1 in the series (M₂Cu₂O₃)_m(CuO₂)_n can be considered as an individual `Cu-deficient ladder-type' structure intermediate between SrCu₂O₃ and incommensurate phases (M₂Cu₂O₃)_m(CuO₂)_n (m n).

Online March 2000

    

Acta Cryst. (2000). A56, 157-162  [ doi:10.1107/S010876739901497X ]

Expansion of scalar validation criteria to three dimensions: the R tensor

S. Parkin

Synopsis: A method to expand conventional scalar validation statistics to three dimansions is described.

Online March 2000

 

Acta Cryst. (2000). A56, 163-167  [ doi:10.1107/S0108767399015068 ]

X-ray diffraction from an atomic plane

W. Yashiro and T. Takahashi

Synopsis: Reflection and transmission coefficients of X-rays by a single atomic plane are obtained in the general case where the plane consists of any two-dimensional Bravais lattice and the incident and exit X-ray beams take any direction with respect to the plane. A formula obtained for the coefficients is written in simple form.

Online March 2000

 

Acta Cryst. (2000). A56, 168-177  [ doi:10.1107/S0108767399015421 ]

The likelihood function in fiber diffraction

X.-Q. Mu and L. Makowski

Synopsis: A cylindrically symmetric model is proposed for the distribution of atomic coordinate errors in helical structures. Formulas for likelihood functions in fiber difraction are presented.

Online March 2000

 

Acta Cryst. (2000). A56, 178-188  [ doi:10.1107/S0108767399015512 ]

Search for isotypism in crystal structures by means of the graph theory

V. A. Blatov

Synopsis: A method for the classification of crystal structures is proposed, which is based on the representation of the interatomic bond system in a crystal as a finite `reduced' graph. The computer program IsoTest realizing this method is described.

Online March 2000

 

Acta Cryst. (2000). A56, 189-192  [ doi:10.1107/S0108767399015433 ]

Measurement of Debye-Waller factors in Co₃Ti by quantitative CBED

M.-Y. Wu, S.-Y. Li, J. Zhu, Z.-H. Du and S.-L. Li

Synopsis: An effective quantitative CBED method was used to obtain the Debye-Waller factors of Co and Ti atoms in Co₃Ti. The results are B_Co = 0.20-0.24 and B_Ti = 0.41-0.43  Å² at room temperature.

Online March 2000

 

Acta Cryst. (2000). A56, 193-225  [ doi:10.1107/S0108767399014002 ]

Report of the Executive Committee for 1998

Online March 2000

 

Acta Cryst. (2000). A56, 226  [ doi:10.1107/S0108767399012374 ]

Patterson peaks

Online March 2000

 

Acta Cryst. (2000). A56, 226  [ doi:10.1107/S0108767399014014 ]

Nonequilibrium phase transitions in lattice models

Online March 2000

 

Acta Cryst. (2000). A56, 226  [ doi:10.1107/S0108767300000908 ]

Supersymmetry in disorder and chaos

Online March 2000