First‐principles Simulations of Glass‐formers

Molecular Dynamics Simulation of Amorphous SiO2, B2O3, Na2O–SiO2, Na2O–B2O3, and Na2O–B2O3–SiO2 Glasses with Variable Compositions and with Cs2O and SrO Dopants

“…The vibrational properties play a significant role in the estimation of specific heat, heat conductance, and transparency of glass. The data shown in Figure e is in agreement with the studies by Kob and Ispas as well as Tanguy et al The VDOS of SiO 2 show a flat peak at 200–600 cm –1 and another peak in between ∼1050 and 1070 cm –1 . The lower frequency peak is known to have originated from the bending and rocking motion of oxygen atoms.…”

“…The results show a slight postshift at 120 cm –1 and a preshift at 1100 cm –1 for doped NBS compared to NBS, which might be associated with the weakening of the Si–O BO –Si network and increasing Si–O NBO with doping of the glass matrix. The reported peak positions can be found in good agreement with the studies reported by Kob and Ispas for the NBS glass matrix. Since the glassy state of a similar NBO shares very similar peak positions, only negligible differences were noticed for doped glasses compared to the NBS glass matrix, however, a significant change can be noticed for NBS or doped NBS matrix compared to the pure glass matrix of SiO 2 and B 2 O 3 .…”

“…It has to be noted that the vibrational frequency of this mode depends on the strength of the O–B–O bond-angle interaction and therefore might deviate slightly for other potential models. Essentially, the selected potential parameters well reproduce the experimental VDOS and earlier reported data. − …”

“…To some extent, the broadening of the lower frequency peak reflects the disordered structure of amorphous SiO 2 ; however, most of the part comes from the inability of the potential model to accurately reproduce the VDOS spectra. The peak broadening is seen to have significantly reduced in the case of first principles studies as well as in the experimental studies of VDOS for SiO 2 . , Nevertheless, such a flat structure of VDOS of SiO 2 at the lower frequency zone is not new but has been reported by many earlier MD simulation studies. , Further, the peaks at higher frequency ∼1050–1070 cm –1 in the VDOS of SiO 2 capture well the modes concerning intra-tetrahedral excitations. Additionally, the VDOS spectrum of B 2 O 3 shows four characteristic peaks at 130, 670, 960  , and 1180 cm –1 .…”

BaO-doped silicate and borosilicate glasses for enhanced chemical durability: molecular dynamics simulations based strategy for glass design

“…11(b) represents the effect of Ba doping on the VDOS spectra of binary BaO–SiO 2 and quaternary Ba-NBS glass. In line with the studies of Kob and Ispas, 100 the NBS glass show major peaks at ∼120 cm −1 and ∼1027 cm −1 along with a broad shoulder at ∼700 cm −1 and a broad peak at ∼430 cm −1 . 60,74 Usually, the lower frequency peaks in the region ∼65–940 cm −1 emerged from the stretching, rocking, and bending motion of Si–O–Si, while the peaks in the intermediate region 400–600 cm −1 originated from the symmetric stretching of the bonding oxygen atoms X–O BO –X (X is the network forming element such as Si and B) as well as from the breathing vibration of four to six-membered rings; on the other hand, the peak at ∼1027 cm −1 is connected with the intra-tetrahedral excitations within SiO 4 /BO 4 .…”