List of PARAMETERS by section

This page lists parameters for ViPErLEED by which section of ViPErLEED/TensErLEED they are (most) relevant for. Parameters may occur multiple times, and not all parameters are listed. See the main PARAMETERS page for a complete alphabetical list and other groupings.

Note

While all parameters have a default value, parameters marked with a “→” usually require user input for simple but non-trivial systems.

Initialization

Parameter	Function
BEAM_INCIDENCE	Incidence angle and direction of the electron beam in experiment
BULK_LIKE_BELOW	Onset of unrelaxed slab, for automatic detection of minimal bulk and bulk repeat
BULK_REPEAT	Thickness of the bulk repeat unit, or a bulk repeat vector
ELEMENT_MIX	Declare that sites in the POSCAR file can be occupied by different chemical elements
LAYER_CUTS	How to separate the POSCAR file into layers
→ N_BULK_LAYERS	Define how many layers in the POSCAR file represent the bulk
→ SITE_DEF	Define which sites in the POSCAR file are special, i.e. have different vibrational amplitude
→ SUPERLATTICE	The relationship between the surface and bulk unit cells
SYMMETRIZE_INPUT	Whether to move atoms in the POSCAR file to perfectly match the symmetry
SYMMETRY_EPS	Error tolerance during symmetry search
SYMMETRY_FIX	Manually set a symmetry, or turn symmetry off
SYMMETRY_FIND_ORI	Whether the symmetry search should look for the highest-symmetry point.
THEO_ENERGIES	What energy range to calculate
T_DEBYE	Debye temperature of the system (only for automatically generating VIBROCC)
T_EXPERIMENT	Measurement temperature in experiment (only for automatically generating VIBROCC)
VIBR_AMP_SCALE	Scaling factor, only for automatically generating VIBROCC

Note

Parameters setting the symmetry strongly affect all sections, but are not listed again below.

Reference calculation

Parameter	Function
ATTENUATION_EPS	Cutoff for beam propagation
BEAM_INCIDENCE	Incidence angle and direction of the electron beam in experiment
BULKDOUBLING_EPS	Convergence criterion for bulk thickness in the TensErLEED calculation
BULKDOUBLING_MAX	Maximum bulk thickness in TensErLEED calculation
BULK_REPEAT	Thickness of the bulk repeat unit, or a bulk repeat vector
ELEMENT_MIX	Declare that sites in the POSCAR file can be occupied by different chemical elements
FILAMENT_WF	The LEED filament work function
KEEP_REFCALC_DIRS	Toggle to keep the reference calculating execution directories
LAYER_CUTS	How to separate the POSCAR file into layers
LMAX	Maximum angular momentum number; usually determined via PHASESHIFT_EPS
→ N_BULK_LAYERS	Define how many layers in the POSCAR file represent the bulk
→ N_CORES	The number of CPUs to use
PHASESHIFT_EPS	Cutoff in phaseshifts magnitudes to determine LMAX
SCREEN_APERTURE	The aperture of the acceptance cone of the LEED screen
→ SITE_DEF	Define which sites in the POSCAR file are special, i.e. have different vibrational amplitude
→ SUPERLATTICE	The relationship between the surface and bulk unit cells
TENSOR_OUTPUT	Disable Tensor output for some or all layers
THEO_ENERGIES	What energy range to calculate
V0_IMAG	Imaginary part of the inner potential
V0_REAL	Real part of the inner potential
V0_Z_ONSET	How far from the topmost atom the inner potential begins

\(R\)-factor calculation

Parameter	Function
BEAM_INCIDENCE	Incidence angle and direction of the electron beam in experiment
IV_SHIFT_RANGE	Range and step size for shifting experimental and theoretical curves during \(R\)-factor calculation
PLOT_IV	Change appearance of the \(R\)-factor plot files
R_FACTOR_TYPE	Which definition of the \(R\) factor to use
R_FACTOR_SMOOTH	How strongly experimental beams are smoothed
→ SUPERLATTICE	The relationship between the surface and bulk unit cells
THEO_ENERGIES	What energy range to calculate
V0_IMAG	Imaginary part of the inner potential

Delta-amplitudes calculation

Behavior is mainly governed by the DISPLACEMENTS file. Some relevant parameters are:

Parameter	Function
ELEMENT_MIX	Declare that sites in the POSCAR file can be occupied by different chemical elements
LMAX	Maximum angular momentum number; usually determined via PHASESHIFT_EPS
→ N_CORES	The number of CPUs to use
PHASESHIFT_EPS	Cutoff in phaseshifts magnitudes to determine LMAX
→ SITE_DEF	Define which sites in the POSCAR file are special, i.e. have different vibrational amplitude
→ SUPERLATTICE	The relationship between the surface and bulk unit cells
TENSOR_INDEX	Which Tensor files to use for the delta calculation and search
THEO_ENERGIES	What energy range to calculate

Search

Behavior is also governed by the DISPLACEMENTS file. The most relevant parameters are:

Parameter	Function
BEAM_INCIDENCE	Incidence angle and direction of the electron beam in experiment
IV_SHIFT_RANGE	Range and step size for shifting experimental and theoretical curves during \(R\)-factor calculation
LOG_SEARCH	Output the search log file (may be very large, mostly for debugging)
→ N_CORES	The number of CPUs to use
R_FACTOR_TYPE	Which definition of the \(R\) factor to use
R_FACTOR_SMOOTH	How strongly experimental beams are smoothed
SEARCH_BEAMS	Whether to use \(R\) factor of integer, fractional, or all beams for the search
SEARCH_CONVERGENCE	Convergence criteria for the search, and convergence-dependent parameter control
SEARCH_CULL	Controls regular culling of worst-performing structures, and what to replace them with
SEARCH_MAX_GEN	Maximum total number of generations that the search should run for
SEARCH_POPULATION	Number of trial structures used in the search
SEARCH_START	How to initialize the search population
STOP	Stop execution of ViPErLEED at next opportunity
TENSOR_INDEX	Which Tensor files to use for the delta calculation and search
THEO_ENERGIES	What energy range to calculate
V0_IMAG	Imaginary part of the inner potential

Domain search

As the domain search may involve all of the segments above, the parameters listed there are relevant. The following additional parameters affect domains specifically:

Parameter	Function
DOMAIN	Define a domain for calculations involving multiple coexisting structural domains
DOMAIN_STEP	Step width for structural domain coverage during search
SYMMETRY_CELL_TRANSFORM	Relationship between a supercell and the primitive surface unit cell (only relevant for domain calculations)