Unit 1 : Basic Concepts of Crystal Structure Flashcards
minerals formed underground from three-dimensional repeating patterns of atoms.
Crystals
the experimental science of determining the arrangement of atoms
in crystalline solids.
Crystallography
a solid material whose constituents (such as atoms, molecules, or ions) are arranged in a highly ordered
A Crystal or Crystalline Solid
The smallest group of particles in the material that constitutes the repeating pattern is the unit cell of the structure.
Unit Cell
describes the periodic repetition of a structural feature across a length or through an area or volume.
Translational symmetry
describes the periodic repetition of a structural feature around a point.
Point symmetry
occurs when the structure features on one side of a plane passing through the center of a crystal are the mirror image of the structural features on the other side.
Reflection
Describes the repetition of a motif or structural feature around a single reference point, commonly the center of a unit cell or a crystal.
Point symmetry
executable shifting movements, proceeding along a straight line and on a certain specified distance, such that the operation does not result in any change of the shifted pattern.
Translational symmetry
arises when a structural element is rotated a fixed number of degrees about a central point and then repeated.
Rotational symmetry
any line which is drawn through the origin at the center of the crystal will connect two identical features on opposite sides of the Reflection in a point (Center of Symmetry)
inversion symmetry
a compound symmetry operation which is produced by performing a rotation followed by an inversion.
Rotoinversion
The crystal class which possesses the highest possible symmetry or the highest number of symmetry elements within each system is
holomorphic class
a set of faces which are geometrically equivalent and whose spatial positions are related to one another according to the symmetry of the crystal.
Crystal form
also called a pedion. It consists of a single face which is geometrically unique for the crystal and is not repeated by any set of symmetry operations.
Monohedron
also called a pinacoid. It consists of two and only two geometrically equivalent faces which occupy opposite sides of a crystal.
Parallelohedron
consists of two and only two nonparallel geometrically equivalent faces.
Dihedron
possess two sets of nonparallel geometrically equivalent faces, each of which is related by a 2-fold rotation.
Disphenoid
composed of a set of 3, 4, 6, 8, or 12 geometrically equivalent faces which are all parallel to the same axis.
Prism
composed of a set of 3, 4, 6, 8, or 12 faces which are not parallel but instead intersect at a point.
Pyramid
composed of two pyramids placed base-to-base and related by reflection across a mirror plane which runs parallel to and adjacent
to the pyramid bases.
Dipyramid
the ability of a solid material to exist in more than one form or crystal structure.
polymorphism
