I am calculating the energy of the system using quantum espresso.
The input file I am using to relax Mo structure is attached to this thread.
While the calculations are taking place, I observed that "Energy error" is oscillating and the cell parameters are reducing continusely. For different "etot_conv_thr" values, I am getting errors such as change cell_factor, "eigenvalues not converged", "charge is wrong".
How to handle these errors?
Dear Rajendra Prasad Gorrey,
I looked at your input file, and it contains two errors:
1) If you specify "alat" in the CELL_PARAMETERS, all those values are multiplied by the constant A or celldm(1). In your case, if you specify as celldm the value of the lattice constant, the CELL_PARAMETERS must be either 1 or -1.
2) The value of the degauss establishes an effective electronic temperature. That value should be relatively small. Setting it to 0.2 might introduce a systematic error. Try reducing it.
The celldm(1) parameter you set seems too large to me. So I would expect that QE reduces it significantly (by reducing the CELL_PARAMETERS in output). A large change in the unit cell parameters might reduce the accuracy of the calculations. For example, the k-points are defined in the initial unit cell. Using a large cell_factor might help in performing a unit cell optimisation, but then you should run an SCF calculation with the new unit cell and check that the other physical parameters remain well converged.
Finally, you set a press=0 requirement for the relaxation. This is an impossible target, and QE will stop without attaining it.
I hope this helps,
Roberto
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