Checking Convergence

Several parameters can be used as convergence criteria. The first criterion is map quality. A map with coefficients $(3F_o-2F_c / 2mF_o-DF_c,\alpha_c)$ is calculated from the last ARP model. The crystallographic R factor is a reasonable quantity to monitor.

What to do if the R factor stays at the values around 30%:
(Check with something like grep 'all_R' logs/1_arp_1.log) If for example after 5 or 10 cycles, R dropped to 28-34% and stayed there for the next 10 cycles without any tendency to drop further, you may be in trouble. Try to change from Fast to Slow protocol or opposite, try to introduce phase restraints, change advanced parameters, panic, cry, etc.! We are working on more sensible suggestions all the time, so as a last resort contact us! Your feedback is needed and appreciated!