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At and mol further

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  • How does the energy change when one decreases SIGMA to 0.001 in the INCAR file starting from the [[O_atom? Why?
  • Try to play with the parameter POTIM for the example O_dimer. What is the optimal value?
  • What is the reason for the imaginary frequency in the example CO_vibration? Does the behaviour improve when the step width (smaller or larger) is changed? Also try to improve the precision to which the ground state is converged (EDIFF=1E-5). What happens if the accuracy of the calculations is improved (PREC=Accurate).
  • Try to use the conjugate gradient algorithm to the molecule (example H2O).
  • Calculate the vibrational frequencies of the molecule (example H2O) after relaxation (example H2O vibration). Why does one find 3 modes that have small frequencies? Try EDIFF=1E-5 instead of EDIFF=1E-4.