Improved empirical force field for multicomponent oxide glasses and crystals

Abstract

widely used for the simulation of a large variety of silicates, aluminosilicate and phosphate crystals, and multicomponent oxide glasses have been revised and improved by the inclusion of two types of three-body interactions acting between T-O-T bridges (T = Si and P) and network former-network former repulsive interactions. The FFs named Bertani-Menziani-Pedone (BMP)-harm and BMP-shrm better reproduce the T-O-T bond angle distributions (BADs) and network former-oxygen distances. Consequently, the prediction of Q n distributions (Q stands for quaternary species, and n is the number of bridging oxygens around it), neutron total distribution functions, solid-state nuclear magnetic resonance spectra of spin active nuclei ( 29 Si, 17 O, 31 P, 27 Al), and the density have also been hugely improved with respect to the previous version of our FF. These results also highlight the strong correlation between the T-O-T BADs and the other short and intermediate structural properties in oxide glasses, which have been largely neglected in the past. In addition to the improvement of the structure, the FF has been revealed to reproduce well the ionic conductivity in mixed alkali aluminosilicate glasses and the elastic properties. The systematic comparison with other interatomic potential models, including the polarizable core-shell model, carried out in this paper showed that our potential model is more balanced and effective for simulating a vast family of crystalline and amorphous oxide-based systems.

A new self‐consistent empirical potential model for multicomponent borate and borosilicate glasses

“…The Stevensson-Edén potential has not been tested on this property because we have realized in a previous investigation that the density is not a reproduce well with the actual parameterizations of core-shell potential. 36 As for the NBS glasses, the BMP reliably reproduce the trend of the density with increasing R values, leading to an MAE of 0.06 g/cm 3 on the complete NBS series. The formula and methods used to simulate the neutron diffraction total distribution functions are reported in the Supporting Information of our previous work 36 as well as in Refs.…”

“…36 As for the NBS glasses, the BMP reliably reproduce the trend of the density with increasing R values, leading to an MAE of 0.06 g/cm 3 on the complete NBS series. The formula and methods used to simulate the neutron diffraction total distribution functions are reported in the Supporting Information of our previous work 36 as well as in Refs. [104,105].…”

“…Only the θ ijk value of the three-body interaction was kept fixed at 109.47 • as it is for all the triplets already parameterized. 36 The choice of the reference angle was biased by the sp 3 hybridization of BO atoms, derived from the valence bond theory. 70,71 According to this theory, BO atoms have four surrounding electron pairs, two of which are bonding pairs and two are lone pairs, ideally oriented along the vertices of a tetrahedron with angles of 109.47 • .…”

“…To better sample the parameter space, we used different initial parameters D, a, r 0 , and k. The initial B-O, B-O-Si, and B-O-B parameters ranged between 0.8 ≤ D ≤ 2.8, 2.0 ≤ a ≤ 3.5, 1.4 ≤ r 0 ≤ 1.6, and 10 ≤ k ≤ 100, whereas the starting A and ρ parameters of the repulsive B-B and B-Si Buckingham interaction were set to the analogs Si-Si parameters of the BMP potential. 36 From this fitting, an initial set of parameters was obtained for further refinement (D = 1.06223 eV, a = 2.60414 Å −2 , r 0 = 1.543656 Å, 𝑘 B−O−B = 60 eV/rad 2 , 𝑘 B−O−Si = 60 eV/rad 2 , A B-B = 8.9594 eV and ρ B-B = 0.8012 Å −1 , A B-Si = 8.9594 eV and ρ B-Si = 0.9270 Å −1 ). These parameters were tested on the sodium borate (NBR) series but give poor results on the BO 3 /BO 4 speciation (see Figure 2) because of the very complex boron chemistry in glasses that cannot be fully parameterized using only crystalline structures.…”

“…In this work, the BMP force-field 36,37 (from author surnames Bertani-Menziani-Pedone), a potential recently developed by some of us as the evolution of the PMMCS 38,39 (Pedone-Malavasi-Menziani-Cormack-Segre) one, has been extended to multicomponent borate and borosilicate glasses.…”