Program CELSLC > Dr. Probe / Documentation

 

The program CELSLC is used to calculate object transmission functions aka. phase gratings from atomic structure models. Files describing the atomic structure and other parameters are specified as arguments upon calling. The output is organized in so-called slice files, which are input for multislice calculations with the program MSA or the Dr. Probe GUI.

In order to calculate the elastic forward scattering of the incident electron by the electrostatic potential of the atomic structure, the crystal potential is projected to planes from very thin volume slices in the multislice approach. The elastic scattering potentials are calculated using the parameterization of Weickenmeier and Kohl [Acta Cryst. A47 (1991) p. 590-597] or alternatively those of Waasmaier and Kirfel [Acta Cryst. A51 (1995) p. 416-431]. CELSLC allows you also to use alternative or individual atomic form factors. Please contact the developer for more detailed explanations if you are interested.

Projected potentials of each structure slice are transformed to phase gratings describing the phase shift of the probing electron wave function caused by the screened Coulomb potentials of the atomic core charges. The program supports the calculation of phase gratings with different atomic configurations to model effects of thermal vibrations or to apply Debye-Waller factors and absorptive potentials to account for the effect of phonon excitations on elastic electron scattering.

Two different options are provided to apply absorptive potentials:

1. Absorptive potentials according to Weickenmeier & Kohl [Acta Cryst. A47 (1991) p. 590-597] or Hall & Hirsch [Proc. R. Soc. Lond. A 286 (1957) 158–177] describing the loss of electrons in the elastic channel. The option is available when applying Debye-Waller factors.
2. Constant user defined absorption parameter, as proposed by Hashimoto, Howie, and Whelan [Proc. R. Soc. London Ser. A, 269 (1962) p. 80-103] describing a loss of electrons relative to the scattering strength of an atom. Typical values are on the range from 0.01 to 0.20.

Example: Multiple atomic configurations of periodic periodic SrTiO₃ [001] for HAADF-STEM image simulations

50 structure variants are calculated for each of 2 structure slices on a 480 x 480 grid for 300 keV. The input structure model consists of 3 x 3 unit cells. The output phase gratings will be stored in the files STO001-300kV_001.sli and STO001-300kV_002.sli.

celslc -cel STO_001_3x3.cel -slc STO001-300kV -nx 480 -ny 480 -nz 2 -nv 50 -fl -ht 300

Example: Periodic SrTiO₃ [110] for high-resolution TEM image simulations

Phase gratings are calculated of 4 structure slices are calculated on a 108 x 80 grid for 300 keV electrons with Debye-Waller factors and absorptive form factors. The input structure model consists of 2 SrTiO₃ unit cells in [110] orientation. The output phase gratings will be stored in the files STO110-300kV_001.sli, ..., STO110-300kV_004.sli.

celslc -cel STO_110_2UC.cel -slc STO110-300kV -nx 108 -ny 80 -nz 4 -dwf -abs -ht 300

 

Last update: May 18, 2021    contact    disclaimer(de)