VIBR_AMP_SCALE

VIBR_AMP_SCALE is used when vibrational amplitudes are automatically generated from the T_EXPERIMENT and T_DEBYE parameters. E.g., vibrational amplitudes of the surface atoms are normally larger than in the bulk, so one wants to scale the bulk vibration amplitudes. VIBR_AMP_SCALE will never be used if the VIBROCC file exists and defines a vibrational amplitude for the site in question.

Default: 1.0 for every site

Allowed values: one positive float value per site

Syntax:

VIBR_AMP_SCALE = Fe_surf 1.3, O_surf 1.3
! OR
VIBR_AMP_SCALE = *surf 1.3

Scaling factors can be defined on a single line (comma delimited pairs), or on multiple lines.

The site types are labelled as El_sitename, where El is an element as found in the POSCAR file, and sitename is a site name defined in the PARAMETERS file under SITE_DEF. Asterisks * are treated as wildcard characters, so *surf in the example above will match both Fe_surf and O_surf. (The same convention as in the VIBROCC file.)

In the example above, if the vibrational amplitude for Fe has been calculated to be 0.1 Å, the vibrational amplitude for the Fe_surf atoms will be set to 0.13 Å.

Note

The parameters T_DEBYE, T_EXPERIMENT and VIBR_AMP_SCALE will normally be used only once, to calculate an initial guess for vibrational amplitudes and generate a VIBROCC file. Afterwards, all three parameters will automatically be commented out in the PARAMETERS file; the vibration amplitudes will be defined in the VIBROCC file instead. Even if the parameters were un-commented again, they would never be used as long as a VIBROCC file is present.