What is quasicrystalline geometry?

Quasicrystals are patterns that fill all of a space but do not have the translational symmetry that is characteristic of true crystals. In two dimensions this means that sliding an exact copy of the pattern over itself will never produce an exact match, though rotating the copy will often produce a match.

What is forbidden symmetry?

Symmetry forbidden transition is a term commonly used in the context of electronic spectroscopy. This term refers to the electronic transitions that occur from one quantum to another. The Laporte rule is a spectroscopic selection criterion that is applied to molecules that have an inversion centre and atoms.

How quasicrystals are different from crystals?

The key difference between crystals and quasicrystals is that crystals have an ordered structure that is periodic, whereas quasicrystals also have an ordered structure that is not strictly periodic. The terms crystals and quasicrystals are useful in the field of crystallography that falls under industrial chemistry.

What are quasicrystals good for?

Quasicrystals have been used in surgical instruments, LED lights and non stick frying pans. They have poor heat conductivity, which makes them good insulators.

What is aperiodic crystal?

An aperiodic crystal is a structure with sharp diffraction peaks, but without lattice periodicity. Therefore, amorphous systems are not aperiodic crystals. The positions of the sharp diffraction peaks of an aperiodic crystal belong to a vector module of finite rank.

What are allowed and forbidden transitions?

specification of selection rule Selection rules, accordingly, may specify “allowed transitions,” those that have a high probability of occurring, or “forbidden transitions,” those that have minimal or no probability of occurring.

What is Laporte forbidden transition?

The Laporte rule is a rule that explains the intensities of absorption spectra for chemical species. It is a selection rule that rigorously applies to chromophores that are centrosymmetric, i.e. with an inversion centre. It states that electronic transitions that conserve parity are forbidden.