Neumann’s principle in crystallography

E458004

Neumann’s principle in crystallography is a fundamental rule stating that the symmetry elements of any physical property of a crystal must include the symmetry elements of the crystal’s point group.

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Neumann’s principle 47

Statements (47)

Predicate Object
instanceOf crystallographic principle
physical principle
appliesTo crystals
physical properties of crystals
appliesToPropertyType conductivity tensors
dielectric properties
elastic properties
magnetic properties
optical properties
piezoelectric properties
thermal expansion
assumes crystal described by a point group
category symmetry principle in physics
constraintType symmetry constraint
coreStatement The symmetry elements of any physical property of a crystal must include the symmetry elements of the crystal’s point group.
domainOfApplication linear response properties
nonlinear optical properties
field crystallography
materials science
solid-state physics
holdsFor all 32 crystallographic point groups
implies degeneracies in physical properties follow crystal symmetry
forbidden tensor components must vanish
physical property symmetry cannot be lower than crystal point group symmetry
involvesConcept anisotropy
crystal point group
material symmetry
symmetry elements
tensor properties
mathematicalFormulation property tensors must be invariant under all symmetry operations of the crystal point group
namedAfter Franz Ernst Neumann NERFINISHED
relatedTo Curie’s principle NERFINISHED
representation theory of point groups
tensor transformation laws
relatesSymmetryOf physical properties
relatesSymmetryTo crystal point group symmetry
status widely accepted in crystallography
usedFor constraining physical property tensors
determining allowed tensor components
predicting anisotropy of physical properties
usedIn crystal optics
elasticity theory of crystals
group-theoretical analysis of crystals
magnetocrystalline anisotropy analysis
materials characterization
piezoelectricity analysis
validFor equilibrium physical properties

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Franz Ernst Neumann notableWork Neumann’s principle in crystallography