We investigate the structural and vibrational properties of glassy ${\mathrm{B}}_2{\mathrm{O}}_3$ using first-principles molecular dynamics simulations. In particular, we determine the boroxol rings fraction $f$ for which there is still no consensus in the literature. Two numerical models containing either a low or a high level of boroxol rings are tested against a gamut of experimental probes (static structure factor, Raman, ${}^{11}\mathrm{B}$ and ${}^{17}\mathrm{O}$ NMR data). We show that only the boroxol-rich model ($f=75\%$) can reproduce the full set of observables. Total-energy calculations show that at the glass density, boroxol-rich structures are favored by about $6\mathrm{kcal}/(\mathrm{mol}\mathrm{\text{boroxol}})$. Finally, the liquid state is explored in the 2000–4000 K range and a reduction of $f$ to 10%–20% is obtained.

• Received 12 March 2008

DOI:https://doi.org/10.1103/PhysRevLett.101.065504