Units

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.