# Robust fixed model

I have a question when I apply fixed and random model, then hausman test, the results show that the appropriate one is fixed model based on hausman test, then I want to check the heterocedasticity for the fixed model using xttest3 (modified wald test ) I found that there is an heteroscedasticity to correct it I have added option robust with fixed. Is it sufficient or then I have apply once again hausman, because I already try it I get this message hausman cannot be used with vce(robust) ... Also I have another question is it sufficient to decide between re and fixed model using hausman, can we use for example R2