Convergence-control.md

+# Convergence criteria
+There are two parameters controlling the computation accuracy of the solution:
+```bash
+energyconveps           1.0e-6   # energy convergence epsilon
+                                 # energy changes between two subsequent iteration 
+                                 # expressed in units E_ffg needs to be smaller than npartconveps
+                                 # for converged solution
+                                 # default=1.0e-6
+npartconveps            1.0e-6   # number of particles convergence epsilon
+                                 # relative difference between obtained particle number
+                                 # and total particle number must be smaller than npartconveps
+                                 # for converged solution
+                                 # default=1.0e-6
+```
+
+The solution is regarded as *converged* when all contributions to the energy satisfy `energyconvep` and particle number satisfies criteria `npartconveps`. Info about the status of convergence is printed on standard output.
+Example of a report for converged solution for input parameters:
+```bash
+Na                      17       # requested particle number, spin-a
+Nb                      18       # requested particle number, spin-b
+energyconveps           1.0e-6   # energy convergence epsilon
+npartconveps            1.0e-6   # number of particles convergence epsilon
+```
+may look like:
+```
+# CONVERGENCE REPORT PARTICLE NUMBER: it=58
+    SPINA: NEW=              17 OLD=       17.000003 DIFF=  -3.1644056e-06 CONVSTATUS=  PASS NPARTCONV=   2.1975596e-09
+    SPINB: NEW=       18.000001 OLD=       17.999995 DIFF=   5.4727832e-06 CONVSTATUS=  PASS NPARTCONV=    2.406396e-08
+# CONVERGENCE REPORT ENERGY: it=58
+    E_kin: NEW=        1.879979 OLD=       1.8799781 DIFF=   8.9986865e-07 CONVSTATUS=  PASS
+    E_pot: NEW=     -0.51360103 OLD=     -0.51360098 DIFF=  -4.7134213e-08 CONVSTATUS=  PASS
+   E_pair: NEW=     -0.94237189 OLD=     -0.94237177 DIFF=  -1.2408755e-07 CONVSTATUS=  PASS
+   E_curr: NEW=   3.5892537e-14 OLD=   9.6882531e-14 DIFF=  -6.0989994e-14 CONVSTATUS=  PASS
+ E_potext: NEW=               0 OLD=               0 DIFF=               0 CONVSTATUS=  PASS
+E_pairext: NEW=               0 OLD=               0 DIFF=               0 CONVSTATUS=  PASS
+ E_velext: NEW=               0 OLD=               0 DIFF=               0 CONVSTATUS=  PASS
+  ------------------------------------------------------------------------------------------
+    E_tot: NEW=      0.42400609 OLD=      0.42400536 DIFF=   7.2864682e-07 CONVSTATUS=  PASS
+```
+
+# Ajusting of chemical potentials
+TODO