\newcommand{\dista}[1]{\unit[#1]{\AA}{}}
\newcommand{\perc}[1]{\unit[#1]{\%}{}}
+%\newcommand{\bra}[1]{\left\langle #1 \right|}
+%\newcommand{\ket}[1]{\left| #1 \right\rangle}
+%\newcommand{\braket}[2]{\left\langle #1 \mid #2 \right\rangle}
\newcommand{\bra}[1]{\langle #1 |}
\newcommand{\ket}[1]{| #1 \rangle}
\newcommand{\braket}[2]{\langle #1 | #2 \rangle}
as expected and --- in fact --- obtained from equation~\eqref{eq:solid:so_bs1}.
\end{proof}
-In order to include the spin-orbit interaction into the scalar-relativistic formalism of a normconserving, non-local pseudopotential, scalar-relativistic in contrast to fully relativistic pseudopotential wavefunctions are needed as a basis for the projectors of the spin-orbit potential.
+\subsubsection{Scalar relativistic basis}
+
+In order to include the spin-orbit interaction into the scalar relativistic formalism of a normconserving, non-local pseudopotential, scalar relativistic in contrast to fully relativistic pseudopotential wavefunctions are needed as a basis for the projectors of the spin-orbit potential.
The transformation
\begin{equation}
L\cdot S=L_xS_x+L_yS_y+L_zS_z
It acts on all magnetic quantum numbers and updates all of them.
\end{enumerate}
Please note that the $\ket{l,m,\pm}$ are not eigenfunctions of the two combinations of ladder operators, i.e.\ the $\ket{l,m,\pm}$ do not diagonalize the spin-orbit part of the Hamiltonian.
-(Does this constitute a problem?)
+These equations can be simplified to read
+\begin{eqnarray}
+\ldots
+\text{ .}
+\end{eqnarray}
+
+\subsubsection{A different basis set}
+
+The above basis is composed of eigenfunctions
+\begin{equation}
+\ket{l,m} \text{, } \ket{\pm} \text{ of operators }
+L^2\text{, } L_z \text{ and } S_z
+\text{.}
+\end{equation}
+These eigenfunctions diagonalize the scalar relativistic Hamiltonian.
+Introducing spin-orbit interaction, however, it is a good idea to chose eigenfunctions that diagonalize the perturbation
+\begin{equation}
+L\cdot S=\frac{1}{2}(J^2-L^2-S^2)
+\text{ ,}
+\end{equation}
+i.e.\ simultaneous eigenfunctions of $J^2$, $L^2$ and $S^2$.
\subsubsection{Excursus: Real space representation within an iterative treatment}