Molecular Dynamics Analysis of the Microstructure of the CaO-P₂O₅-SiO₂ Slag System with Varying P₂O₅/SiO₂ Ratios

Abstract

The structures of the CaO-P 2 O 5 -SiO 2 slag system with varying P 2 O 5 /SiO 2 ratios at a fixed CaO content have been investigated by molecular dynamics simulation using the pairwise potential model. The results showed that the average bond lengths of Si-O and P-O were 1.610 « 0.001 ¡ and 1.531 « 0.005 ¡ in the examined range of the P 2 O 5 /SiO 2 ratio. More than 95% Si and P ions were 4-coordinated and formed tetrahedral structures. Average coordination numbers of P-O and Si-O decreased slightly while average coordination number of Ca-O revealed a rising trend with the addition of P 2 O 5 . The non-bridging oxygens (Si-O-Ca and P-O-Ca) were the overwhelming majority and further increased with the substitution of SiO 2 by P 2 O 5 , which results in the decrease of the polymerization constant K p . The numbers of Si and P groups linked to a tagged Si or P tetrahedron (Q n speciation) characterized the polymerization degree of the slag system. The Q 0 of both P and Si declined remarkably with the increase of P 2 O 5 . Correspondingly, () of Si and P increased observably, implying that the polymerization degree of the slag system was enhanced.

Paramagnetic Intrinsic Point Defects in Alkali Phosphate Glasses: Unraveling the P3 Center Origin and Local Environment Effects

“…At variance with the RMC-SP model made of 100% Q 2 units, as expected for the NaPO 3 glass, , we note that models obtained by means of classical molecular dynamics are not so realistic as they contain sizeable fractions of Q 1 and Q 3 units. , In fact, the appearance of Q 1 and Q 3 is intrinsically related to the CMD atomistic description based on simple interaction potentials. , Moreover, the presence of Q 5 units is also likely to be an artifact of classical molecular dynamics. , Although we are not aware of any experimental data about Q 5 units in alkali phosphate glasses, we remark that Q 5 units might appear in melt phases . However, from a macroscopic dielectric point of view, the presence of a few Q 1 , Q 3 , and Q 5 units in CMD-SP does not substantially alter its dielectric response.…”

“…52,60 Moreover, the presence of Q 5 units is also likely to be an artifact of classical molecular dynamics. 61,62 Although we are not aware of any experimental data about Q 5 units in alkali phosphate glasses, we remark that Q 5 units might appear in melt phases. 63 However, from a macroscopic dielectric point of view, the presence of a few Q 1 , Q 3 , and Q 5 units in CMD-SP does not substantially alter its dielectric response.…”

Effect of the Initial P Content on Dephosphorization of Hot Metal with Low Basicity Slag at 1623 K

“…where X ðMOÞ represents the mole fraction of MO in molten slag. K P is the equilibrium constant of Reaction (8). C PO 3À 4 can be calculated with Equation ( 10) and (11).…”

“…There were some reports on the effect of the P 2 O 5 content in slag on the viscosity and microstructure of molten slag. [3][4][5][6][7][8][9][10] For example, Wang et slag increase. [10] Sun et al also reported that the viscosities of CaO-SiO 2 -Al 2 O 3 -MgO-TiO 2 -P 2 O 5 slags with the basicity of 0.5-0.97 increase substantially with increasing the P 2 O 5 addition amounts, in which P 2 O 5 acts as a characteristic network former in the melts.…”

Viscosity of molten CaO K2O SiO2 woody biomass ash slags in relation to structural characteristics from molecular dynamics simulation

“…They do, however, collectively suggest prospects of good correlations between structural characteristics and slag viscosity. Others have also used MD simulations to elucidate structural features like pair distribution functions (PDFs) and bond/bridging angles between atoms [18][19][20]. Such common structural characteristics may be related to the viscosity of slags because they contain attributes that reflect aspects of atomic mobility in the silicate network.…”