Phonons selection

Selecting Phonons on the Properties tab displays options for calculating phonon properties.

Density of states: When selected, computes the phonon density of states as part of the CASTEP run.

Dispersion: When selected, computes the phonon dispersion as part of the CASTEP run.

Both: When selected, computes both the phonon density of states and dispersion during the CASTEP run.

Calculate LO-TO splitting: When selected, applies a non-analytical correction to the dynamical matrix. This calculates the LO-TO phonon frequency splitting at the Γ-point along the directions connecting the Γ-point with the neighboring points along the reciprocal space path. Default = checked.

Method: Select the technique to use to calculate phonon frequencies. Available options are:

• Linear response
• Finite displacement

Finite displacement phonons are available only at the commensurate q-points (at the cost of creating a supercell). However, in this case, you can obtain the phonon frequencies with no limitations on the settings so that, for example, you can use ultrasoft potentials.

If you request LO-TO splitting, then the restrictions on the system type and settings (insulator, norm-conserving potentials) are the same for both the linear response and finite displacement techniques.

More...: Provides access to the CASTEP Phonon Properties Setup dialog, where you can specify additional parameters affecting a phonon calculation, including the convergence tolerance.

Access methods

Menu	Modules | CASTEP | Calculation | Properties | Phonons
Toolbar	| Calculation | Properties | Phonons

See Also:

Properties tab - CASTEP Calculation dialog
Requesting vibrational properties
Phonons