CASTEP Properties

The CASTEP Properties task allows you to compute electronic, structural, and vibrational properties after the completion of a single-point energy, geometry optimization, or dynamics run on a 3D periodic system.

To calculate properties using the CASTEP Properties task, the results files from a suitable simulation must be present in the current project.

You can also use the Properties tab on the CASTEP Calculation dialog to request calculation of such properties as part of a CASTEP run. You can view the results using the CASTEP Analysis dialog.

The properties that CASTEP can generate are:

Band structure: This calculates electronic eigenvalues along high symmetry directions in the Brillouin zone. These calculations are non-self-consistent for both valence and conduction bands, using electronic charge densities and potentials generated during the simulation.
Core level spectroscopy: This calculates electronic energies on the Monkhorst-Pack mesh of k-points and the matrix elements for electronic interband transitions, either with or without core holes.
Density of states: This calculates electronic eigenvalues on a fine Monkhorst-Pack grid . These calculate are non-self-consistent for both valence and conduction bands, using electronic charge densities and potentials generated during the simulation.
Electron density difference: This calculates the electron density difference with respect to a linear combination of either the atomic densities or the densities of sets of atoms contained in the structure.
Electron localization function: This calculates a simple measure of electron localization in atomic and molecular systems.
Electronic excitations (TD-DFT): This calculates electronic excitations for molecules in a box, using the time-dependent density functional theory (TD-DFT).
NMR: This calculates chemical shielding tensors, electric field gradients, J-couplings, and g-tensors.
NMR in CASTEP is part of the separately licensed module NMR CASTEP. NMR calculations can only be performed if you have purchased this module.
Optical properties: This calculates matrix elements for electronic interband transitions . The CASTEP Analysis dialog allows you to generate grid and chart documents containing measurable optical properties.
Orbitals: This provides information about electronic wavefunctions. This allows you to visualize 3D distribution of various electronic states (orbitals). Visualization of STM profiles also requires this information.
Phonons: For phonon dispersion runs, this calculates phonon frequencies and eigenvectors along high symmetry directions in the Brillouin zone. In the case of phonon density of states calculations, this computes phonon frequencies and eigenvectors on a Monkhorst-Pack grid. Analysis requires this information to display total and projected (partial) phonon densities of states. Calculation of thermodynamic properties including atomic displacement parameters also uses this information. This allows assignment of temperature factors during analysis.
Phonon calculations take into account existing fixed atom constraints, regardless of the overall Task setting. Calculation of vibrational properties does not include such fixed atoms, corresponding to the "partial Hessian" approach.
Select the Fix fractional position checkbox on the Atom tab of the Edit Constraints dialog, accessible from the Modify menu.
Polarizability, IR and Raman spectra: This calculates the optical (ω = ∞) and dc (ω = 0) dielectric permittivity or the optical (ω = ∞) and static (ω = 0) molecular polarizability, along with infrared or Raman intensities (response to an electric field in the infrared range). Permittivity is relevant for solid materials, while polarizability and infrared intensities are relevant to molecules prepared using the supercell approach.
Population analysis: This performs Mulliken analysis and Hirshfeld charge analysis. This includes calculation of Mulliken bond populations and angular momentum-resolved atomic charges (as well as magnetic moments for spin-polarized calculations, and production of Hirshfeld atomic charges. Optionally, CASTEP can generate the weights required for partial density of states (PDOS) calculations.
Solvation energy: This calculates the free energy of solvation and writes it to a seedname_Solv.castep file. CASTEP automatically prepares calculations using vacuum and implicit solvation schemes and extracts solvation energy from the respective energies of these two calculations.
Stress: This calculates the stress tensor and writes it to a seedname.castep file. This information is useful if, for example, you perform a geometry optimization run with fixed cell parameters and you want to verify how far the lattice is from equilibrium. For example, carry out a supercell study of a point defect with the fixed cell that corresponds to the theoretical ground state of the given system. The value of the stress after geometry optimization gives an indication of the magnitude of the elastic effects associated with the supercell approximation.

CASTEP Properties

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