Surface Structure of Hydroxyapatite from Simulated Annealing Molecular Dynamics Simulations
Surface Structure of Hydroxyapatite from Simulated Annealing Molecular Dynamics Simulations
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模拟退火分子动力学模拟中羟基磷灰石的表面结构
DOI：
10.1021/acs.langmuir.5b04667
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发表时间：
2016
期刊：
影响因子：
3.9
通讯作者：
Zhang Xingdong
中科院分区：
文献类型：
--
作者：
Wu Hong;Xu Dingguo;Yang Mingli;Zhang Xingdong
羟基磷灰石（HAP）的表面结构对其生物活性至关重要。采用分子动力学模拟退火方法，研究了HAP（100）表面的结构及其随退火温度的变化。与常用的HAP表面模型相比，该模型是从HAP晶体上切片，然后通过第一原理或力场计算在0 K下松弛，揭示了一种从内部有序到表面无序逐渐变化的新表面结构。无序度取决于退火温度 Tmax。当Tmax增加到熔点时（实验中通常采用这种方法），无序度会增加，这可以通过其径向分布函数、结构因素和原子配位数反映出来。当 Tmax 高于熔点时，退火结构的无序度没有表现出显着变化。无序层的厚度约为10 Å。高温退火结构的表面能明显小于室温松弛晶体结构的表面能。随后提出了内部、中间和表面三层模型来描述 HAP 的表面结构。内层保留了晶体中的原子构型。中间层的原子移动，其基团围绕其原始位置旋转。表层的原子排列与晶体中的原子排列完全不同。特别是对于羟基，它们向外移动并覆盖 Ca2+ 离子，留下被磷酸基团占据的孔。我们的研究提出了一种具有无序表面结构的新模型，用于研究基于 HAP 的生物材料与其他分子的相互作用。
The surface structure of hydroxyapatite (HAP) is crucial for its bioactivity. Using a molecular dynamics simulated annealing method, we studied the structure and its variation with annealing temperature of the HAP (100) surface. In contrast to the commonly used HAP surface model, which is sliced from HAP crystal and then relaxed at 0 K with first-principles or force-field calculations, a new surface structure with gradual changes from ordered inside to disordered on the surface was revealed. The disordering is dependent on the annealing temperature,Tmax. WhenTmaxincreases up to the melting point, which was usually adopted in experiments, the disordering increases, as reflected by its radial distribution functions, structural factors, and atomic coordination numbers. The disordering of annealed structures does not show significant changes whenTmaxis above the melting point. The thickness of disordered layers is about 10 Å. The surface energy of the annealed structures at high temperature is significantly less than that of the crystal structure relaxed at room temperature. A three-layer model of interior, middle, and surface was then proposed to describe the surface structure of HAP. The interior layer retains the atomic configurations in crystal. The middle layer has its atoms moved and its groups rotated about their original locations. In the surface layer, the atomic arrangements are totally different from those in crystal. In particular for the hydroxyl groups, they move outward and cover the Ca2+ions, leaving holes occupied by the phosphate groups. Our study suggested a new model with disordered surface structures for studying the interaction of HAP-based biomaterials with other molecules.