@article{GorfmanTsirelsonPietsch2005,
  author    = {Gorfman, S. V. and Tsirelson, Vladimir G. and Pietsch, Ullrich},
  title     = {X-ray diffraction by a crystal in a permanent external electric field : general considerations},
  issn      = {0108-7673},
  year      = {2005},
  abstract  = {The variations of X-ray diffraction intensities from a crystal in the presence of a permanent external electric field is modeled analytically using a first-order stationary perturbation theory. The change in a crystal, induced by an external electric field, is separated into two contributions. The first one is related to a pure polarization of an electron subsystem, while the second contribution can be reduced to the displacements of the rigid pseudoatoms from their equilibrium positions. It is shown that a change of the X-ray diffraction intensities mainly originates from the second contribution, while the influence of the pure polarization of a crystal electron subsystem is negligibly small. The quantities restored from an X-ray diffraction experiment in the presence of an external electric field were analyzed in detail in terms of a rigid pseudoatomic model of electron density and harmonic approximation for the atomic thermal motion. Explicit relationships are derived that link the properties of phonon spectra with E-field-induced variations of a structure factor, pseudoatomic displacements and piezoelectric strains. The displacements can be numerically estimated using a model of independent atomic motion if the Debye - Waller factors and pseudoatomic charges are known either from a previous single-crystal X-ray diffraction study or from density functional theory calculations. The above estimations can be used to develop an optimum strategy for a data collection that avoids the measurements of reflections insensitive to the electric-field-induced variations},
  language  = {en}
}
@article{PietschTsirelsonGorfan2003,
  author    = {Pietsch, Ullrich and Tsirelson, Vladimir G. and Gorfan, S. V.},
  title     = {X-ray scattering amplitude of an atom in a permanent external electric field},
  year      = {2003},
  language  = {en}
}
@article{TsirelsonAbramovZavodniketal.1998,
  author    = {Tsirelson, Vladimir G. and Abramov, Yury Fedorovich and Zavodnik, Valerie E. and Stash, Adam I. and Belokoneva, Elena L. and Stahn, Jochen and Pietsch, Ullrich and Feil, Dirk},
  title     = {Critical pionts in a crystal an procrystal},
  year      = {1998},
  language  = {en}
}
@article{AvilovKulyginPietschetal.1999,
  author    = {Avilov, Anatoly S. and Kulygin, Alexander K. and Pietsch, Ullrich and Spence, John C. H. and Tsirelson, Vladimir G. and Zuo, Ming J.},
  title     = {Scanning system for high-energy electron diffractometry},
  issn      = {0021-8898},
  doi       = {10.1107/S0021889899006755},
  year      = {1999},
  language  = {en}
}
@article{AvilovLepeshovPietschetal.2001,
  author    = {Avilov, Anatoly S. and Lepeshov, G. G. and Pietsch, Ullrich and Tsirelson, Vladimir G.},
  title     = {Multipole analysis of the electron density and electrostatic potential in Germanium by high-resolution electron diffraction},
  issn      = {0022-3697},
  year      = {2001},
  language  = {en}
}
@article{TsirelsonAvilovLepeshovetal.2001,
  author    = {Tsirelson, Vladimir G. and Avilov, Anatoly S. and Lepeshov, G. G. and Kuligin, A. K. and Stahn, Jochen and Pietsch, Ullrich and Spence, J. C. H.},
  title     = {Quantitative Analysis of the Inner-Crystal Electrostatic Potential of several Rock-Salt-Structure Crystals Using Accurate Electron-Diffraction Data},
  issn      = {1089-5647},
  year      = {2001},
  language  = {en}
}
@article{GorfmanTsirelsonPucheretal.2006,
  author    = {Gorfman, Semen and Tsirelson, Vladimir and Pucher, Andreas and Morgenroth, Wolfgang and Pietsch, Ullrich},
  title     = {X-ray diffraction by a crystal in a permanent external electric field : electric-field-induced structural response in alpha-GaPO4},
  issn      = {0108-7673},
  doi       = {10.1107/S0108767305036111},
  year      = {2006},
  abstract  = {For the first time, site-selective distortion has been investigated for two different structural units in the ternary compound alpha-GaPO4 under the influence of a permanent external electric field. Based on 54 measured reflection intensities, the electric-field-induced distortion of PO4 and GaO4 tetrahedra in alpha-GaPO4 crystals is evaluated using a model of pseudoatomic displacements introduced recently [Gorfman, Tsirelson \& Pietsch (2005). Acta Cryst. A61, 387- 396]. A stronger variation of the P-O bond lengths in the PO4 tetrahedron was found compared to the bonds in the GaO4 tetrahedron. The different distortions of the tetrahedra owing to the electric field were analysed in terms of the valence charge density of alpha-GaPO4 and its topological characteristics. The larger charge of the P pseudoatom compared to the Ga atom was recognized as the main reason for the higher sensitivity of the PO4 tetrahedron to a permanent external electric field},
  language  = {en}
}