To obtain a simulated diffraction pattern, fill in the field below. After entering the first field, more fields will appear to enter parameters for each layer in the sample. You can also create a plot of the lattice sum for the structure you enter. To plot the lattice sum, complete the form as explained and then complete the last two fields regarding the range of angles and discretization of the plot and click 'Lattice Sum'. An explanation of each field can be found in the Documentaion tab. At the bottom of this page are several sample parameters to which the diffraction pattern can be quickly simulated.
If you want to run the simulation for a superlattice structure, enter the number of layers within the repeating superlattice. Then enter the parameters for each layer in the repeating superlattice from top to bottom and enter the total number of superlattice layers.
Otherwise, to run the simulation for a non-repeating structure, just enter the total number of layers in the field below. Then enter the parameters for each layer in the sample and in the 'number of repeating superlattice layers' field enter 1 to specify that the structure is not repeating.
Simulation Instructions
An explanation of each of the input parameters to run the diffraction simulation are listed below along with parameters for two example structures.
Number of Layers - The sample is made of layers of different materials stacked in the out of plane direction, each with different thickness. This field asks for how many of these different layers are in the sample. If the structure is a superlattice, enter the number of layers of materials within the repeating superlattice layer. The value entered must be a positive integer.
Inlude Substrate - Choose yes or no wheather or not to include the substrate in the sample for the simulation of the diffraction pattern. If the substrate is included the material and lattice constants for the substrate will be added to the simulation inputs
Material - In order of depth, from bottom to top, select the material for the substrate and each layer in the sample or repeating superlattice.
Substrate Out of Plane and In Plane Lattice Constant - Enter the substrate lattice constant in the direction of the surface normal in Angstroms and 90° from the surface normal.
Out of Plane Lattice Constant - In order of depth, from bottom to top, enter the value of the lattice constant in the direction of the surface normal in Angstroms for each layer in the sample or repeating superlattice. The value entered must be a positive number. Typical lattice constant values for all the materials in this simulation will be ~5 Å.
Number of Unit Cells - In order of depth, from bottom to top, enter the number of unit cells in the out of plane direction. The value entered must be a positive integer.
Number of repeating superlattice layers - In a superlattice, a pattern of layers of different materials are repeated one or more times. This field asks for the total number of these repeating cells in the sample. If the structure you are entering is not a superlattice, enter 1 to specify that the strucutre does not repeat. The value entered must be a positive integer.
Angle of Incidence - The angle that the center of the incoming beam makes with the surface of the sample. As this angle is varied, only the l value in reciprocal space is changed. That is, as the angle is varied, the simulation observes along the (00l) direction in reciprocal space. The value entered must be a positive number between 0 and 90 degrees. For the dynamical curve simulation, this will be the center of the range of angles in the plot.
Logarithmic or Linear - Choose wheather the color bar scale for intensity will be logarithmic or linear. For a diffrction pattern the logarithmic color bar should be chosen
Sample Guidelines
Multilayer Stucture
A schematic of a simple two layer structure is shown at right.
For this structure, the input parameters with the information given would be:
Number of layers: 2
Material for Layer 1: A
Number of Unit Cells for Layer 1: 6
Material for Layer 2: B
Number of Unit Cells for Layer 2: 9
Number of Repeating Superlattice Layers: 1* (* 1 here indicates that it is not a superlattice structure)
Superlattice Structure
A schematic of a simple superlattice structure is shown at right.
For this structure, the input parameters with the information given would be:
