Crystallography polarisation

  • What is crystal polarization?

    the macroscopic electric polarization of a crystal cannot be unambiguously defined as the dipole of a unit cell.
    The only measurable quantities are either derivatives of the polarization (dielectric susceptibility, Born effective charges, piezoelectricity, pyroelectricity) or finite differences (ferroelectricity)..

  • What is polarization factor?

    The factor ( 1 + cos 2 2 θ ) / 2 is known as the polarization factor, and as can be seen from Eq. (5.14), this modifies the otherwise inverse-square dependence of I on r..

  • What is polarization in crystal?

    the macroscopic electric polarization of a crystal cannot be unambiguously defined as the dipole of a unit cell.
    The only measurable quantities are either derivatives of the polarization (dielectric susceptibility, Born effective charges, piezoelectricity, pyroelectricity) or finite differences (ferroelectricity)..

  • What is the effect of polarization on diffraction?

    When there is a 'polarization effect' in the diffraction pattern a disclination in the electric field becomes a moving helix or, more generally, a coiled coil.
    As it moves it sweeps out a surface on which the polarization is everywhere linear..

  • What is the factor of polarization?

    The factor ( 1 + cos 2 2 θ ) / 2 is known as the polarization factor, and as can be seen from Eq. (5.14), this modifies the otherwise inverse-square dependence of I on r..

  • What is the Lorentz-polarization factor in XRD?

    The Lorentz-polarization factor is the most impor- tant of the experimental quantities that control X-ray intensity with respect to diffraction angle.
    Its evalua- tion is essential to any analysis that depends on the intensities of X-ray diffraction maxima..

  • The Lorentz correction means a multiplication of the scattering intensities by a factor proportional to the sine of the diffraction angle.
  • The Lorentz–polarization factor is an important component of peak intensity, but it has little or no effect on peak shape except at low diffraction angles and the Lorentz–polarization factor is a factor whose values are controlled by the geometry of the instrument and the preferred orientation of crystallites within
Materials are polarised along a unique crystallographic direction, in that certain atoms are displaced along this axis, leading to a dipole moment along it. Depending on the crystal system, there may be few or many possible axes.
Polarisation may be defined as the total dipole moment per unit volume, i.e. Materials are polarised along a unique crystallographic direction, in that certain atoms are displaced along this axis, leading to a dipole moment along it. Depending on the crystal system, there may be few or many possible axes.

Overview

An optic axis of a crystal is a direction in which a ray of transmitted light suffers no birefringence(double refraction)

Liquid crystal directors

The mobile axis of a liquid crystal is called a director

See also

• Crystal optics• Index


Categories

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