add some documentation

Author: moritzgubler

src/qmoperators/one_electron/ZoraOperator.h

@@ -31,8 +31,22 @@ namespace mrchem {
 
 class QMPotential;
 
+/**
+ * @class ZoraOperator
+ * @brief Implements chi = kappa - 1 relativistic dampening function. This has to be done in order to
+ * avoid numerical instabilities in the ZORA operator. Whenever this operator is applied, the + 1 has to be added to chi i
+ * in order to get the kappa operator. kappa * phi = chi * phi + phi
+ * This has to be done manually.
+ */
 class ZoraOperator final : public RankZeroOperator {
 public:
+    /**
+     * @brief Constructor for the ZoraOperator that contains the chi = kappa - 1 function.
+     * @param vz The potential used to calculate the kappa function.
+     * @param c Speed of light.
+     * @param proj_prec The precision of the MW projection.
+     * @param inverse If true, the inverse of the chi function is calculated.
+     */
     ZoraOperator(QMPotential &vz, double c, double proj_prec, bool inverse = false);
 };