Correlating the structure and dynamics of borophosphate glasses: molecular dynamics approach

O El Kssiri and S Aqdim and A El Bouari and A Tahiri and A Faik and M Filali and M Naji, EUROPEAN PHYSICAL JOURNAL PLUS, 140, 892 (2025).

DOI: 10.1140/epjp/s13360-025-06706-1

Employing molecular dynamics simulations, we investigate the structural evolution in sodium borophosphate glasses (35Na2O-65xB2O3-(1-x)P2O5\documentclass12ptminimal \usepackageamsmath \usepackagewasysym \usepackageamsfonts \usepackageamssymb \usepackageamsbsy \usepackagemathrsfs \usepackageupgreek \setlength\oddsidemargin-69pt \begindocument$ $35\textNa_2\textO-65x\textB_2\textO_3-(1- x)\textP_2\textO_5$$\enddocument). Our simulations reveal that boron coordination shifts from predominantly four-fold (B4\documentclass12ptminimal \usepackageamsmath \usepackagewasysym \usepackageamsfonts \usepackageamssymb \usepackageamsbsy \usepackagemathrsfs \usepackageupgreek \setlength\oddsidemargin-69pt \begindocument$$\textB<^>4$$\enddocument) to mixed three/four- fold (B3/B4\documentclass12ptminimal \usepackageamsmath \usepackagewasysym \usepackageamsfonts \usepackageamssymb \usepackageamsbsy \usepackagemathrsfs \usepackageupgreek \setlength\oddsidemargin-69pt \begindocument$$B<^>3/B<^>4$$\enddocument) configurations with increasing boron content. The dominant P-O-B4\documentclass12ptminimal \usepackageamsmath \usepackagewasysym \usepackageamsfonts \usepackageamssymb \usepackageamsbsy \usepackagemathrsfs \usepackageupgreek \setlength\oddsidemargin-69pt \begindocument$$P-O-B<^>4$$\enddocument linkages facilitate homogeneous network integration at intermediate compositions (x=0.4-0.5\documentclass12ptminimal \usepackageamsmath \usepackagewasysym \usepackageamsfonts \usepackageamssymb \usepackageamsbsy \usepackagemathrsfs \usepackageupgreek \setlength\oddsidemargin-69pt \begindocument$$x=0.4-0.5$$\enddocument), while higher boron concentrations promote B4-O-B3\documentclass12ptminimal \usepackageamsmath \usepackagewasysym \usepackageamsfonts \usepackageamssymb \usepackageamsbsy \usepackagemathrsfs \usepackageupgreek \setlength\oddsidemargin-69pt \begindocument$$B<^>4-O-B<^>3$$\enddocument connectivity and polymerization. Crucially, radial distribution functions and coordination analysis demonstrate that charge-compensating Na+\documentclass12ptminimal \usepackageamsmath \usepackagewasysym \usepackageamsfonts \usepackageamssymb \usepackageamsbsy \usepackagemathrsfs \usepackageupgreek \setlength\oddsidemargin-69pt \begindocument$$\textNa<^>+$$\enddocument ions exhibit delocalized bonding environments around B4\documentclass12ptminimal \usepackageamsmath \usepackagewasysym \usepackageamsfonts \usepackageamssymb \usepackageamsbsy \usepackagemathrsfs \usepackageupgreek \setlength\oddsidemargin-69pt \begindocument$$\textB<^>4$$\enddocument units, with Na-O\documentclass12ptminimal \usepackageamsmath \usepackagewasysym \usepackageamsfonts \usepackageamssymb \usepackageamsbsy \usepackagemathrsfs \usepackageupgreek \setlength\oddsidemargin-69pt \begindocument$$Na-O$$\enddocument coordination increasing from 5.4 (x=0\documentclass12ptminimal \usepackageamsmath \usepackagewasysym \usepackageamsfonts \usepackageamssymb \usepackageamsbsy \usepackagemathrsfs \usepackageupgreek \setlength\oddsidemargin-69pt \begindocument$$x=0$$\enddocument) to 7. 9 (x=1\documentclass12ptminimal \usepackageamsmath \usepackagewasysym \usepackageamsfonts \usepackageamssymb \usepackageamsbsy \usepackagemathrsfs \usepackageupgreek \setlength\oddsidemargin-69pt \begindocument$$x=1$$\enddocument). This structural reorganization reduces non-bridging oxygens and creates new hoping site that enhance ionic conductivity. Our atomistic insights establish a direct correlation between P-O-B\documentclass12ptminimal \usepackageamsmath \usepackagewasysym \usepackageamsfonts \usepackageamssymb \usepackageamsbsy \usepackagemathrsfs \usepackageupgreek \setlength\oddsidemargin-69pt \begindocument$$P-O-B$$\enddocument connectivity, sodium-ion delocalization, and macroscopic ion transport, providing a foundation for designing optimized borophosphate glass electrolytes.

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