Charge Cube File Unit

[mohataba]

Dear all,

I have two questions regarding the BADER charge analysis software and I would be really grateful if someone takes time to guide me:

1-As you may already know, the SIESTA program outputs charge density files as "grid" files and there is a program called "grid2cube" which converts these files to cube format which is required as input by the BADER program. The unit of charge density in the resulting cube files is "electrons/Bohr^3". Does this unit affect my results? Do I have to convert the unit to "electrons/Angstroms^3" to obtain correct and meaningful results?

2-According to the BADER's manual under "-vac" option "Vacuum density cutoff is 1E-3 e/Ang^3 by default". How does the BADER software know whether the input charge density cube file is in "electrons/Angstroms^3" or in "electrons/Bohr^3"? Or it just considers values smaller than 1E-3 (without units) as vacuum?

Bests,
Mohammad,

[graeme]

1. The cube files are read as e/Bohr^3. You do not need to do any conversion.

2. Upon reading a cube file, the code internally converts the charge density file to e/Ang^3 so that the units of the vacuum charge are always e/Ang^3.