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

We present a first-principles investigation of paramagnetic centers in P2 O5 based on the calculation of electron paramagnetic resonance (EPR) parameters (g -tensor and Fermi contacts). Calculations of the EPR parameters for the P1 configuration in crystalline $o'$(P2 O5) support the previous attribution of the P1 to a P-defect structurally analogous to the Si-${E'}$ center. As far as concerns the P1 center in glassy P2 O5, the present work suggests the possible occurrence of another configuration besides the analogue of the Si-${E'}$ center. Such an alternative P1 center configuration is likely to be relevant for those P2 O5 based glasses featuring a considerable fraction of Q1 and Q2 tetrahedral units besides the Q3 unit which dominates the structure of pure P2 O5.