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--- documentation:simulation_modes [2011/09/22 19:08] – 142.103.140.43
+++ documentation:simulation_modes [2015/09/09 08:59] (current) – macke
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+=====Simulation algorithms=====
+===Overview of the different algorithms implemented===
+__Parratt__
+  * For optical isotropic material
+  * Very fast
+  * very stable algorithm
+  * can calculate only sigma- and pi-light. Circluar polarization modelled as average of sigma- and pi-light.
+  * magnetic contributions are included approximately for circular polarized light.
+  * The magnetic dichroism in the Parratt formalism is implemented by changing the magnetization of the sample. Because of the limitations of Parratt a dichroism by changing the polarization of the light is not possible.
+__Zak__
+  * For optical isotropic material with magnetic contributions
+  * very slow
+  * stable algorithm
+  * arbitrary polarization of incident light
+  * top layer must be vacuum for calculating reflectivity
+  * top and bottom layer must be vacuum for calcuting transmission
+  * magnetization can have any direction in the material
+  * The magnetic dichroism is implemented by changing the polarization of the light. A change of the magnetization is not possible. Due to symmetry of the XMCD effect this is not a limitation.
+__Matrix__
+  * For optical anisotropic material which can contain every effect that can be modelled by a dielectric tensor (e. g. magnetism, crystal structure, orbitals)
+  * very slow
+  * algorithm can be numerically unstable
+  * arbitrary polarization of incident light
+  * top layer must be vacuum for calculating reflectivity
+  * top and bottom layer must be vacuum for calcuting transmission
+====Simulation modes====
+The reflectivity is a function of <m>R(q_z, E)</m> with the
+wave vector <m>q_z = 2 k_0 sin(theta)</m>, angle of incidence <m>theta</m> and energy E. Several simulation modes are implemented to calculate the proper reflectivity.
+==Reflectivity==
+__monochromatic__\\
+  * Calculates the reflectivity <m>R(q_z)</m> for a given polarization and energy of the incoming light.
+  * The polarization is defined as "Ray 1" in the "Polarzation" tab.
+  * The energy is defined in the "Reflectivity Settings" tab.
+__dichroic__ \\
+  * Calculates the reflectivity <m>R(q_z)</m> for two given polarizations and one constant energy of the incoming light.
+  * The polarizations are defined as "Ray 1" and "Ray 2" in the polarzation tab.
+  * The energy is defined in the "Reflectivity Settings" tab.
+__asymmetry__\\
+  * Calculates the asymmetry <m>A(q_z)</m> for two given polarizations and one constant energy of the incoming light. The asymmetry is defined as: \\ <m>A={R^{+} - R^{-}} / {R^{+} + R^{-}} </m>\\ \\
+  * The polarizations are defined as "Ray 1" and "Ray 2" in the polarzation tab.
+  * The energy is defined in the "Reflectivity Settings" tab.
+==Energy Scan==
+__monochromatic__\\
+__dichroic__\\
+__asymmetry__\\
+==map==
+__monochromatic__\\
+  * Calculates the reflectivity <m>R(q_z, E)</m> of the sample for a given polarization and energy of the incoming light.
+  * The polarization is defined as "Ray 1" in the "Polarzation" tab.
+  * The energy is defined in the "Reflectivity Settings" tab.
+====Options====
+There are several options to alter the behaviour of the algorithms
+==Option Algorithm==
+Here you can choose the algorithm for the simulation\\
+__Parrat__: activates the parratt algorithm \\
+__Full matrix formalism__: activates matrix algorithm \\
+__Zak matrix formalism__: activates zak algorithm \\
+==Option Precision==
+The algorithm are implemented with different accuracies. For most systems the precision "double" is sufficient.
+In most cases the precision option is only useful for the full matrix formalism because it can be numerically unstable.
+__float__: uses the accuracy of the 4-byte floating point numbers \\
+__double__: uses the accuracy of the 8-byte floating point numbers \\
+__long double__: uses the accuracy of the 10-byte floating point numbers \\
+__60 digits__: uses a floating point numbers with an accuracy of 60 digits. (Very slow, but very accurate)
+===roughness calculation===
+The interface roughness makes your model real. ReMagX uses a model known as Nevot&Croce which defines the interface with
+a continuous change of the optical constants delta and beta.
+__Nevot&Croce__: Use a very efficient model to simulation interface roughness.  \\
+__layer segmentation__: Enable layer segmentation (see chapter "Adaptive Layer Segmentation")