title: Comment on "Pressure-induced structural and valence transition in AgO" by C. Hou, J. Botana, X. Zhang, X. Wang and M. Miao, Phys. Chem. Chem. Phys., 2016, 18, 15322.
abstract: The recent article by Hou et al. has focused on a theoretical study of mixed valence compound AgO in order to elucidate the nature of the electronic structure of this system as a function of external pressure. The authors claim that '…the effects of pressure on the Ag valence state are not investigated yet.' This statement is incorrect in view of the theoretical study published in 2015 by Włodarska et al., which answers most of the questions posed by these authors, including the key one: '…does the Ag cation exhibit similar behaviour to the Au cation in M2Au2X6halides, experiencing mixed-valence to single-valence transition under pressure? If so, what is the mechanism?'.
authors.affiliation: Center of New Technologies, University of Warsaw, Żwirki i Wigury 93, 02089 Warsaw, Poland. mariana@icm.edu.pl w.grochala@cent.uw.edu.pl.
authors.forename: Mariana
authors.initials: M
authors.lastname: Derzsi
authors.affiliation: Center of New Technologies, University of Warsaw, Żwirki i Wigury 93, 02089 Warsaw, Poland. mariana@icm.edu.pl w.grochala@cent.uw.edu.pl.
authors.forename: Wojciech
authors.initials: W
authors.lastname: Grochala