Stability of the Dipolar (001) Surface of Hydroxyapatite
Stability of the Dipolar (001) Surface of Hydroxyapatite
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DOI：
10.1021/jp212595d
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发表时间：
2012-03-15
影响因子：
3.7
通讯作者：
Ugliengo, Piero
中科院分区：
文献类型：
--
作者：
Chiatti, Fabio;Corno, Marta;Ugliengo, Piero
采用周期密度泛函方法，采用B3 LYP混合泛函和高斯极化双zeta质量基组，研究了由P6（3）六方晶HA块体衍生的铁电（质子有序）羟基磷灰石HA（001）表面的特征. HA（001）板模型的厚度从1 nm到几乎50 nm的几何形状，表面能，和电子特性的计算，通过保持在小心控制数值误差，由于非常大的系统尺寸。目前的结果表明，铁电OH-取向不妥协的HA（001）表面的稳定性，直到纳米尺度。实际上，43 nm的板厚度，在晶胞中包含2640个原子，表现出0.73 D的跨板的偶极矩，7.60 eV的宽带隙和1.344 J.m（-2）的表面能。由于一维OH-极性阵列周围的Ca 2+和PO 43-部分的电子密度的反极化，没有出现经典宏观极性锌或氧封端的ZnO（0001）表面的“金属化”迹象。这些发现可能与解释为什么在实验上HA纳米晶体沿着原胶原纤维的主轴取向及其晶体学c轴（垂直于{001}晶面家族）有关。
The features of the ferroelectric (proton ordered) hydroxyapatite HA (001) surface as derived from the P6(3) hexagonal HA bulk have been studied by periodic density functional calculations using the hybrid B3LYP functional and Gaussian basis set of polarized double-zeta quality. Geometry, surface energy, and electronic features of HA (001) slab models of thickness from 1 nm to almost SO nm have been computed, by keeping under careful control numerical errors due to the very large system size. The present results reveal that the ferroelectric OH- alignment does not compromise the stability of the HA (001) surface up to the nanometric scale. Indeed, a slab thickness of 43 nm, containing 2640 atoms in the unit cell, exhibits a dipole moment across the slab of 0.73 D, a wide band gap of 7.60 eV, and a surface energy of 1.344 J.m(-2). No sign of "metallization" occurs as for the classical macroscopic polar zinc- or oxygen-terminated ZnO (0001) surfaces, due to counterpolarization of the electronic density of the Ca2+ and PO43- moieties surrounding the monodimensional OH- polar arrays. These findings may be relevant to explain why, experimentally, HA nanocrystals orient along the main axis of the proto-collagen fibrils with their crystallographic c axis (perpendicular to the {001} crystal plane family).