Units

Physical units are defined in the ase/units.py module. Electron volts (eV) and angstroms (Ang) are defined as 1.0. Other units are nm, Bohr, Hartree or Ha, kJ, kcal, mol, Rydberg or Ry, second, fs and kB.

Note

All constants are taken from the 1986 CODATA.

Examples:

>>> from ase.units import *
>>> 2 * Bohr
1.0583545150138329
>>> 25 * Rydberg
340.14244569396635
>>> 100 * kJ/mol
1.0364272141304978
>>> 300 * kB
0.025852157076770025
>>> 0.1 * fs
0.009822693531550318
>>> print '1 Hartree = '+str(Hartree*mol/kcal)+' kcal/mol'

The ase.data module

This module defines the following variables: atomic_masses, atomic_names, chemical_symbols, covalent_radii, cpk_colors and reference_states. All of these are lists that should be indexed with an atomic number:

>>> from ase.data import atomic_names, atomic_masses
>>> atomic_names[92]
'Uranium'
>>> atomic_masses[2]
4.0026000000000002

If you don’t know the atomic number of some element, then you can look it up in the atomic_numbers dictionary:

>>> from ase.data import atomic_numbers, covalent_radii
>>> atomic_numbers['Cu']
29
>>> covalent_radii[29]
1.1699999999999999