Frequently Asked Questions


  1. Am I eligible for an academic license and if so what must I do?
  2. If I am not eligible for an academic license, how can I obtain CASTEP?

Getting Help

  1. Where can I get help running CASTEP?
  2. I posted to the CASTEP email list asking for help but nobody answered. What can I do to get an answer?

Getting started

  1. I have a CIF file of my structure. How can I generate input files for CASTEP?

SCF convergence

  1. What SCF solver methods are available in CASTEP?
  2. My SCF failed to converge. What can I do?

Geometry Optimization

  1. How can I check whether my geometry optimization really converged?
  2. My BFGS geometry optimization did not converge. What can I do?
  3. Which geometry optimization method should I use?
  4. Should I trust the "Estimated frequency and bulk modulus" printed by a geometry optimisation?

Bandstructure and DOS

  1. How can I quickly generate a density-of-states plot?
  2. How can I plot partial densities of states?
  3. How can I generate an electronic density of states with the sharp features I expect?
  4. How can I generate a bandstructure plot?
  5. How can I generate a publication quality electronic band structure with the bands properly joined up?
  6. Why does my OPTADOS density of states plot not look like the one using, even for fixed Gaussian smearing?
  7. My bandstructure looks a mess with many very short segments.
  8. How can I checkpoint and restart a bandstructure calculation?

Phonon and related calculations

  1. How can I calculate phonons for a spin-polarized system?
  2. How can I do a phonon calculation with DFT+D?
  3. My Raman calculation gives huge numbers or nonsense or "*" characters for the intensity. Why?
  4. How can I perform a "mode-following"calculation explore the energy of a function of amplitude for a particular phonon mode?
  5. I performed a phonon DOS calculation. Do I need to repeat all that calculation if I want dispersion curves as well?
  6. How can I generate a phonon DOS with both sharp and curved features as in textbook examples? I just get a wiggly mess from
  7. How can I compute a phonon projected density of states?

Magnetic resonance calculations

  1. For what kind of molecules and crystals can CASTEP provide reliable NMR predictions?
  2. I completed a NMR ab initio simulation, now how can I compare it with my experimental spectra?
  3. How can I checkpoint and restart a MAGRES calculation?


  1. Which pseudopotential library should I use for functionality which only works with norm-conserving pseudopotentials?
  2. What pseudopotential libraries are available for use with CASTEP?

Postprocessing and Visualisation

  1. How can I create an animation of a geometry optimisation or MD trajectory from my calculation??
  2. How can I create an animation of phonon modes from my calculation??
  3. How can I visualise the results of an NMR chemical shift calculation?
  4. How can I visualise electron density or spin density??

Run-time failure messages

  1. My run aborted with a message of the type "Error XXXX: Failed to open YYYY file"
  2. wave_orthonormalise_overlap_wv_ks: ztrtri failed in inversion
  3. Error writing wavefunction coefficients to file in wave_write_all_par
  4. Error reading wavefunction coefficients from file in wave_read_all_par

Interfacing with other codes

  1. How can I convert my CASTEP run output to use the Henkelman Bader analysis code?

General problems getting a run to work

  1. How should I choose the best number of cores for a parallel run on Archer?
  2. My job stopped before it reached the end. How can I find out how and why it failed?
  3. My HECToR/Archer job fails and the the messages in the PBS log file talk about the "OOM Killer". What does this mean?
  4. How many atoms can I sensibly include in my model?
  5. How can I check my input files do not have a mistake before submitting to the batch queue?
  6. How can I find out how much memory my run will use?


  1. I think I found a bug in CASTEP. What should I do?