Ajusting of chemical potentials

Static codes adjust chemical potentials automatically in such a way to provide a solution with requested particle number. Following parameters control adjusting process:

muchange                0.5      # coefficient for changing chemical potential, default=0.5
mumaxchange             0.05     # maximal allowed changed of chemical potential per iteration,
                                 # in units of Fermi energy

Chemical potentials are adjusted according to rule:

\begin{aligned}
\Delta\mu_{\sigma}^{(i)} &= \textrm{muchange}\,\frac{N_{\sigma}^{(\textrm{req.})}-N_{\sigma}^{(i)}}{N_{\sigma}^{(\textrm{req.})}}\\
\textrm{if}\,|\Delta\mu_{\sigma}^{(i)}/\varepsilon_F|&>\textrm{mumaxchange}:\,\textrm{decrease}\,\textrm{magnitude}\,\textrm{of}\,\Delta\mu_{\sigma}^{(i)}\\
\mu_{\sigma}^{(i+1)} &= \mu_{\sigma}^{(i+1)} + \Delta\mu_{\sigma}^{(i)} 
\end{aligned}

Fixed chemical potential mode

In order to execute calculations for fixed chemical potential you need to set in input file:

muchange                0.0      # do not change chemical potential
npartconveps            1.0e+9   # ignore checking of particle number convergence criteria

In addition, you need to set the value of chemical potentials. For this use process_params function in problem-definition.h

void process_params(double *params, double *kF, double *mu, size_t extra_data_size, void *extra_data)
{
   // hard set of chemical potentials
   mu[SPINA] = YOUR_VALUE; // <-- you can promote it as user-defined parameter
   mu[SPINB] = YOUR_VALUE; // <-- you can promote it as user-defined parameter

   // ...
}