Division of Materials, Mechanics and Structures, Faculty of Engineering, University of Nottingham, Nottingham, UK.
J Phys Condens Matter. 2010 Dec 8;22(48):485403. doi: 10.1088/0953-8984/22/48/485403. Epub 2010 Nov 17.
Details of the microscopic structure of phosphate glasses destined for biomedical applications, which include sodium, magnesium and calcium cations, have been obtained from the static structure factor measured by means of neutron scattering. A complementary, molecular dynamics study has been performed on a range of phosphate glasses using density functional theory methods, which allow structural fluctuations, including bond breaking, in the liquid phase before quenching to the glass phase. Good agreement between experiment and simulation allows the molecular dynamics trajectories to be analysed in detail. In particular, attention is focused on the cross-linking of divalent cations in contrast with the structural aspects associated with monovalent cations. Magnesium cations are found equidistant and bridging between the phosphorus atoms of different phosphate chains, leading to a shorter phosphorus-phosphorus second neighbour distance (that is, a more compact packing of neighbouring phosphate chains) compared to the effect of sodium cations. Calcium cations show behaviour intermediate between those of magnesium and sodium. Molecular dynamics simulations give access to the cation mobility, which is lowest for magnesium, reflecting its structural, cross-linking role.
通过中子散射测量静态结构因子，获得了用于生物医学应用的磷酸盐玻璃的微观结构细节，其中包括钠离子、镁离子和钙离子。使用密度泛函理论方法对一系列磷酸盐玻璃进行了补充的分子动力学研究，这些方法允许在淬火到玻璃相之前在液相中进行结构波动，包括键的断裂。实验和模拟之间的良好一致性允许对分子动力学轨迹进行详细分析。特别是，关注的焦点是二价阳离子的交联，与与一价阳离子相关的结构方面形成对比。镁离子在不同磷酸盐链的磷原子之间等距桥接，导致磷-磷第二近邻距离（即相邻磷酸盐链的更紧凑包装）缩短，与钠离子的影响相比。钙离子表现出介于镁离子和钠离子之间的行为。分子动力学模拟可以获得阳离子的迁移率，镁离子的迁移率最低，反映了其结构交联作用。
