Index n refers to an atomic energy level and R refers to an atomic site.
Wannier functions on different atomic sites R are orthogonal.
In this system, an atom is missing from its regular atomic site.
The corresponding spectrum therefore has twelve peaks, a 'hextet' for each potential atomic site.
In the case of an impurity, the atom is often incorporated at a regular atomic site in the crystal structure.
In this approach, interactions between different atomic sites are considered as perturbations.
There are 58 independent atomic sites in the unit cell.
But not until now has the Energy Department taken a coordinated approach to preserving atomic sites.
The second are the special inspections, requiring a country to open up an area it has not declared as an atomic site.
Environmental activists have broken into a French nuclear power station, to highlight the "vulnerability" of atomic sites in France.