I want to use the formation energy formula used by the article in the picture below. The authors have used the term S or Sn-rich environment. What is the meaning of this? How it is related to the calculation of formation energy? Reference paper : https://doi.org/10.1063/1.5022151

I am currently looking for an efficient way to detect common functional groups - that is, characterize whether a molecule is an alcohol, an aromatic compound, etc. - in a larger database consisting of xyz geometry files. Is there an existing tool out there that could do this task? I am aware that...