U

Name UnfoldEnergyStep
Section Utilities::oct-unfold
Type float
Default 0

Specifies the energy resolution for the unfolded band structure. If you specify 0, the resolution will be set to be 1/1000 points between UnfoldMinEnergy and UnfoldMaxEnergy

Name UnfoldKPointsPath
Section Utilities::oct-unfold
Type block

Specifies the k-point path for which the unfolding need to be done. The syntax is identical to KPointsPath.

Name UnfoldLatticeParameters
Section Utilities::oct-unfold
Type block

The lattice parameters of the primitive cell, on which unfolding is performed. See the LatticeParameters variable for a more detailed description.

Name UnfoldLatticeVectors
Section Utilities::oct-unfold
Type block
Default simple cubic

Lattice vectors of the primitive cell on which the unfolding is performed. See the LatticeVectors variable for a more detailed description.

Name UnfoldMaxEnergy
Section Utilities::oct-unfold
Type float

Specifies the end of the energy range for the unfolded band structure. The default value correspond to the largest eigenvalue.

Name UnfoldMinEnergy
Section Utilities::oct-unfold
Type float

Specifies the start of the energy range for the unfolded band structure. The default value correspond to the samllest eigenvalue.

Name UnfoldMode
Section Utilities::oct-unfold
Type flag
Default none

Specifies which stage of the unfolding tool to use

Options:

• unfold_setup:
  Writes the list of k-points corresponding to the path specified by UnfoldKPointPath. This list of k-point (unfold_kpt.dat) must be used for an unocc calculation of the supercell, adding the line "include 'unfold_kpt.dat'" to the inp file and removing the KPointGrid information.
  
• unfold_run:
  Perform the actual unfolding, based on the states obtained from the previous unocc run.
  

Name Units
Section Execution::Units
Type virtual
Default atomic

(Virtual) These are the units that can be used in the input file.

Options:

• angstrom:
  
• pm:
  
• picometer:
  
• nm:
  
• nanometer:
  
• ry:
  
• rydberg:
  
• ev:
  
• electronvolt:
  
• invcm:
  
• kelvin:
  
• kjoule_mol:
  
• kcal_mol:
  
• as:
  
• attosecond:
  
• fs:
  
• femtosecond:
  
• ps:
  
• picosecond:
  
• c:
  

Name UnitsOutput
Section Execution::Units
Type integer
Default atomic

This variable selects the units that Octopus use for output.

Atomic units seem to be the preferred system in the atomic and molecular physics community. Internally, the code works in atomic units. However, for output, some people like to use a system based on electron-Volts (eV) for energies and Angstroms (Å) for length.

Normally time units are derived from energy and length units, so it is measured in $\hbar$/Hartree or $\hbar$/eV.

Warning 1: All files read on input will also be treated using these units, including XYZ geometry files.

Warning 2: Some values are treated in their most common units, for example atomic masses (a.m.u.), electron effective masses (electron mass), vibrational frequencies (cm^-1) or temperatures (Kelvin). The unit of charge is always the electronic charge e.

Options:

• atomic:
  Atomic units.
  
• ev_angstrom:
  Electronvolts for energy, Angstroms for length, the rest of the units are derived from these and $\hbar=1$.
  

Name UnitsXYZFiles
Section Execution::Units
Type integer
Default angstrom_units

This variable selects in which units I/O of XYZ files should be performed.

Options:

• bohr_units:
  The XYZ will be assumed to be in Bohr atomic units.
  
• angstrom_units:
  XYZ files will be assumed to be always in Angstrom, independently of the units used by Octopus. This ensures compatibility with most programs, that assume XYZ files have coordinates in Angstrom.
  

Name UnoccShowOccStates
Section Calculation Modes::Unoccupied States
Type logical
Default false

If true, the convergence for the occupied states will be shown too in the output. This is useful for testing, or if the occupied states fail to converge. It will be enabled automatically if only occupied states are being calculated.

Name UnoccUseTD
Section Calculation Modes::Unoccupied States
Type logical
Default no

If true, Octopus will use the density and states from the restart/td folder to compute the bandstructure, instead of the restart/gs ones.

Name UseAllAtomicOrbitals
Section Hamiltonian::DFT+U
Type logical
Default no

If set to yes, Octopus will determine the effective U for all atomic orbitals from the peusopotential. Only available with ACBN0 functional. It is strongly recommended to set AOLoewdin=yes when using the option.

Name UserDefinedConstantSpatialMaxwellField
Section Maxwell
Type block

Define parameters of spatially constant field.

Example:

%UserDefinedConstantSpatialMaxwellFields
   plane_wave_parser | E_x | E_y | E_z | B_x | B_y | B_z | "tdf_function"
%

This block defines three components of E field, three components of B field, and reference to the TD function.

Name UserDefinedInitialMaxwellStates
Section Maxwell
Type block

The initial electromagnetic fields can be set by the user with the UserDefinedMaxwellStates block variable. The electromagnetic fields have to fulfill the Maxwells equations in vacuum.

Example:

%UserDefinedMaxwellStates
   formula | 2 | "magnetic_field" | "-1/P_c * sin(x)"
   formula | 3 | "electric_field" | " sin(x) "
%

The second column specifies the component of the dimension of the electric field and magnetic field. The first column indicates that column four should be interpreted as a formula for the corresponding state. P_c is the speed of light constant.

Alternatively, if column one states file the electric field and magnetic field will be read from the files given in column four.

%UserDefinedMaxwellStates
   file | 3 | electric_field | "/path/to/file_electric_field_of_dimension_3"
   file | 2 | magnetic_field | "/path/to/file_magnetic_field_of_dimension_2"
%

The third option to define the initial state inside the box is to extend the plane waves used as incident waves in the MaxwellIncidentWaves block, as follows:

%UserDefinedMaxwellStates
   use_incident_waves
%

Options:

• file:
  Read initial orbital from file. Accepted file formats: obf, ncdf and csv.
  
• formula:
  Calculate initial orbital by given analytic expression.
  
• use_incident_waves:
  Extend the plane waves given in the MaxwellIncidentWaves block inside the box.
  
• electric_field:
  This row defines the electric field component of the corresponding dimension
  
• magnetic_field:
  This row defines the magnetic field component of the corresponding dimension
  

Name UserDefinedMaxwellExternalCurrent
Section Maxwell
Type block

Example:

%UserDefinedMaxwellExternalCurrent
   current_parser | "expression_x_dir1" | "expression_y_dir1" | "expression_z_dir1"
   current_parser | "expression_x_dir2" | "expression_y_dir2" | "expression_z_dir2"
   current_td_function | "amplitude_j0_x" | "amplitude_j0_y" | "amplitude_j0_z" | omega | envelope_td_function_name | phase
%

Description about UserDefinedMaxwellExternalCurrent follows

Options:

• current_parser:
  description follows
  
• current_td_function:
  description follows
  

Name UserDefinedStates
Section States
Type block

Instead of using the ground state as initial state for time-propagations it might be interesting in some cases to specify alternate states. Like with user-defined potentials, this block allows you to specify formulas for the orbitals at t=0.

Example:

%UserDefinedStates
   1 | 1 | 1 | formula | "exp(-r^2)exp(-i0.2*x)" | normalize_yes
%

The first column specifies the component of the spinor, the second column the number of the state and the third contains k-point and spin quantum numbers. Column four indicates that column five should be interpreted as a formula for the corresponding orbital.

Alternatively, if column four states file the state will be read from the file given in column five.

%UserDefinedStates
   1 | 1 | 1 | file | "/path/to/file" | normalize_no
%

Octopus reads first the ground-state orbitals from the restart/gs directory. Only the states that are specified in the above block will be overwritten with the given analytic expression for the orbital.

The sixth (optional) column indicates whether Octopus should renormalize the orbital. The default (no sixth column given) is to renormalize.

Options:

• file:
  Read initial orbital from file. Accepted file formats, detected by extension: obf, ncdf and csv (real only).
  
• formula:
  Calculate initial orbital by given analytic expression.
  
• normalize_yes:
  Normalize orbitals (default).
  
• normalize_no:
  Do not normalize orbitals.