List of PARAMETERS by topic

This page lists parameters for ViPErLEED by grouping them into categories. 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.

`viperleed.calc` execution

Defines what to calculate and where to start.

Parameter	Function
HALTING	Sensitivity to things going wrong, i.e. how easily should ViPErLEED stop
→ RUN	Which parts of ViPErLEED / TensErLEED should be run, in order
STOP	Stop execution of ViPErLEED at next opportunity
TENSOR_INDEX	Which Tensor files to use for the delta calculation and search
TENSOR_OUTPUT	Disable Tensor output for some or all layers
THEO_ENERGIES	What energy range to calculate
TL_VERSION	Which version of TensErLEED to use
TL_IGNORE_CHECKSUM	Skip calculation of TensErLEED source code checksums

Input structure

Parameter	Function
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
LAYER_CUTS	How to separate the POSCAR file into layers
→ N_BULK_LAYERS	Define how many layers in the POSCAR file represent the bulk
→ SUPERLATTICE	The relationship between the surface and bulk unit cells

Elements, vibrational amplitudes and element concentrations

Parameter	Function
ELEMENT_MIX	Declare that sites in the POSCAR file can be occupied by different chemical elements
ELEMENT_RENAME	Declare that an element in the POSCAR file is actually a different chemical element
→ SITE_DEF	Define which sites in the POSCAR file are special, i.e. have different vibrational amplitude
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

Symmetry determination and control

Parameter	Function
SYMMETRIZE_INPUT	Whether to move atoms in the POSCAR file to perfectly match the symmetry
SYMMETRY_BULK	Manually set the symmetry to be used in beam averaging for the bulk, ignoring automatic detection
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.

Experimental setup

Parameter	Function
AVERAGE_BEAMS	Set beam averaging to assume an incidence other than BEAM_INCIDENCE
BEAM_INCIDENCE	Incidence angle and direction of the electron beam in experiment
FILAMENT_WF	The LEED filament work function
SCREEN_APERTURE	The aperture of the acceptance cone of the LEED screen

Inner potential

Parameter	Function
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

Computational setup

Parameter	Function
FORTRAN_COMP	Which Fortran compiler to use, and tags for compiling
→ N_CORES	The number of CPUs to use

\(R\) factor

Parameter	Function
IV_SHIFT_RANGE	Range and step size for shifting experimental and theoretical curves during \(R\)-factor calculation
R_FACTOR_TYPE	Which definition of the \(R\) factor to use
R_FACTOR_LEGACY	Use legacy TensErLEED \(R\) factor
R_FACTOR_SMOOTH	How strongly experimental beams are smoothed

Search behavior

Parameter	Function
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 parallel during the search
SEARCH_START	How to initialize the search population
OPTIMIZE	Controls behavior of full-dynamic optimization runs

Structural domains

Parameter	Function
DOMAIN	Define domains 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)

TensErLEED approximations

Parameter	Function
ATTENUATION_EPS	Cutoff for beam propagation
BULKDOUBLING_EPS	Convergence criterion for bulk thickness in the TensErLEED calculation
BULKDOUBLING_MAX	Maximum bulk thickness in TensErLEED calculation
LMAX	Maximum angular momentum number; usually determined via PHASESHIFT_EPS
PHASESHIFT_EPS	Cutoff in phaseshifts magnitudes to determine LMAX

Debugging

Parameter	Function
KEEP_REFCALC_DIRS	Toggle to keep the reference calculating execution directories
LAYER_STACK_VERTICAL	How to choose layer stacking vectors in the TensErLEED input (debugging functionality only)
LOG_LEVEL	Set verbosity of the log file
LOG_SEARCH	Output the search log file (may be very large, mostly for debugging)
SUPPRESS_EXECUTION	Generate TensErLEED input files, but stop ViPErLEED before executing TensErLEED (for debugging)

Output style

Parameter	Function
PLOT_IV	Change appearance of the \(R\)-factor plot files

All PARAMETERS