Warning, fitting failed.

[jxsun-netizen]

When calculating the phonon spectrum at high temperature, the following error is displayed: Warning, fitting failed. What is the reason?

[abelcarreras]

This happens because the phonon-mode projected power spectrum is too noisy and the peak corresponding to the phonon mode couldn't be fitted by a Loretzian spectral function. If this fitting fails the anharmonic phonon frequency can't be determined and dynaphopy shows this message.

The way to fix this is by improving the power spectrum. This can be done by:

1. increasing the number of time steps of the MD. For a fix resolution dynaphopy uses long trajectories to average different power spectrums to reduce the noise.

2. Changing the power spectrum calculation method (MEM, FFT, etc..). Usually MEM requires more time steps than FFT.

3. Increase the number of discarded initial stabilization steps to ensure that the MD is properly converged.