Lattice-periodic plane wave
= Lattice-periodic plane wave
{title2=$e^{i\mathbf k\cdot\mathbf R}=1$}
A <plane wave> whose phase is unchanged by every direct lattice translation: $e^{i\mathbf k\cdot\mathbf R}=1$ for all $\mathbf R\in\Lambda$. Its <wavevector> is a <reciprocal lattice vector>. In one dimension $ka=2\pi m$.