First-Principles Investigation of Paramagnetic Centers in P2 O5 Based Glasses

We present a first-principles investigation of paramagnetic centers in P
₂
O
₅
based on the calculation of electron paramagnetic resonance (EPR) parameters (g -tensor and Fermi contacts). Calculations of the EPR parameters for the P
₁
configuration in crystalline $o'$(P
₂
O
₅
) support the previous attribution of the P
₁
to a P-defect structurally analogous to the Si-${E'}$ center. As far as concerns the P
₁
center in glassy P
₂
O
₅
, the present work suggests the possible occurrence of another configuration besides the analogue of the Si-${E'}$ center. Such an alternative P
₁
center configuration is likely to be relevant for those P
₂
O
₅
based glasses featuring a considerable fraction of Q
₁
and Q
₂
tetrahedral units besides the Q
₃
unit which dominates the structure of pure P
₂
O
₅
.