(P2O5)∞ unit cell from x-ray diffraction at 288 K.32 Phosphorus atoms in purple and oxygen atoms in red.
Surface plot of error functions F.Q.(lattice) (upper panel) and F.Q.(bonds) (lower panel) against A and ρ two-body parameters for P–O s interaction (C = 0.03 eV Å6). Static optimization of (P2O5)∞ with all other interactions as stated in Table I. Data cursors show location of minima.
P–O radial distribution function.
O–O and P–P radial distribution functions.
O–P–O and P–O–P angular distribution functions. P–O cutoff set at 2.00 Å.
Na–O and Ca–O radial distribution functions.
O–Na–O and O–Ca–O angular distribution functions associated with first coordination spheres. Na–O and Ca–O cutoffs set at 3.15 Å and 3.22 Å, respectively.
Ca2+ pseudo-octahedral bonding environment. Snapshot from P45C35N20 trajectory at 300 K. Calcium atoms in green, sodium atoms in deep purple, phosphorus atoms in light purple, and oxygen atoms in red.
Formal charge shell-model force field used in this work. Buckingham two-body, harmonic three-body, and core-shell potentials.
Dominant shell frequencies and corresponding amplitudes for different damping coefficient parameterization. Sample core-shell unit at 2500 K.
Compositions simulated. (P2O5)0.45(CaO)x(Na2O)0.55−x.
Lattice parameters (Å), unit cell volume (), and associated percentage errors (compared with experiment), of various structures simulated with our force field.
0 K optimization. o ′(P 2 O 5)∞ bond lengths (Å), three-body angles (°) and second order elastic constants (GPa) with associated percentage errors (compared with experiment).
300 K dynamics. Selected average distances, r (Å) and angles, θ (°). (P2O5)∞ Experimental x-ray diffraction (XRD) results given as comparison.
300 K dynamics. Selected average distances (Å) and angles (°). (P2O5)0.45(CaO)x(Na2O)0.55−x (x = 0.30, 0.35 and 0.40). Experimental data, obtained via neutron (ND) and x-ray (XRD) diffraction along with nuclear magnetic resonance (NMR), for a range of vitreous phosphate systems are given for comparison.
Modifier coordination environments. Na–O and Ca–O cut-offs set at 3.15 Å and 3.22 Å respectively.
Qn species distribution (%) for phosphorus with respect to oxygen. Network connectivity (NC) and mean phosphorus coordination (Pc). Experimental data derived from 31P MAS NMR spectra11 given for comparison.
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