Rare-earth site distributions in R(PO₃)₃(R = La,Nd,Er,Yb) metaphosphate glasses by reverse Monte Carlo simulations

Abstract

The R−R pair distribution functions of rare-earth metaphosphate glasses R(PO 3 ) 3 with R = La, Nd, Er, Yb are determined from total X-ray and neutron scattering data by the Reverse Monte Carlo method.

Structure of ultraphosphate glasses with small rare-earth ions by X-ray diffraction

“…The observations were verified by molecular dynamics simulations [37]. Reverse Monte Carlo (RMC) based on X-ray and neutron diffraction data show the decrease of the fraction of short R-R distances for RP 3 O 9 glasses with R = La, Nd, Er, Yb, with decreasing R 3+ ion size [38]. The RMC pair correlations of the ErP 3 O 9 glass [38] broadly agree with those of the TbP 3 O 9 glass [36,37].…”

“…Reverse Monte Carlo (RMC) based on X-ray and neutron diffraction data show the decrease of the fraction of short R-R distances for RP 3 O 9 glasses with R = La, Nd, Er, Yb, with decreasing R 3+ ion size [38]. The RMC pair correlations of the ErP 3 O 9 glass [38] broadly agree with those of the TbP 3 O 9 glass [36,37]. Diffraction experiments which would show the predicted lack of short R-R distances for ultraphosphate glasses of x =~0.16 are difficult due to the small R 2 O 3 fractions and, thus, small weight of the R-R correlations.…”

The structure of calcium metaphosphate glass obtained from x-ray and neutron diffraction and reverse Monte Carlo modelling

“…The FSDP is frequently considered to be indicative of structural correlations over medium range length scales. For example, the FSDP in rare earth metaphosphate glasses is associated with rare earth-rare earth correlations [28]. The present RMC model enables us to examine the contribution to i (Q) from different interatomic correlations.…”

“…MD modelling of phosphate glass has been very limited, being reported only for Li [17], Na [18], Mg, Zn and Pb [19], and Tb [20] metaphosphate glasses. RMC modelling has been more common, being reported for Zn, Sr, Ba, Na and K [21], Li [22], Mg and Co [23], K [24], Zn [25][26][27] and lanthanides [28,29]. There has only been one reported model for Ca metaphosphate glass in 1987, [21], being a preliminary RMC study which used only x-ray diffraction data.…”

A molecular dynamics model of the atomic structure of dysprosium alumino-phosphate glass

“…The previous MD study of Tb metaphosphate glass showed an R • • • R correlation with a small peak around 3.9 Å with nTb Tb = 0.9 and a larger peak around 6.1 Å with nTb Tb = 7.7 [24]. Recent work by Hoppe using reverse Monte Carlo modelling of Er meta-phosphate glass [30] also showed an R • • • R correlation with main feature at 6.2 Å having nR R = 7.14 and a second smaller feature at 4.3 Å having nR R = 0.8.…”