Acid-base properties of hydroxyapatite(0001) by the adsorption of probe molecules: Anab initioinvestigation,Physical Review Materials

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Acid-base properties of hydroxyapatite(0001) by the adsorption of probe molecules: Anab initioinvestigation
Physical Review Materials ( IF 3.1 ) Pub Date : 2021-07-26 , DOI: 10.1103/physrevmaterials.5.075003
Albert F. B. Bittencourt ₁ , Paulo C. D. Mendes ₂ , Gustavo P. Valença ₁ , Juarez L. F. Da Silva ₂

Affiliation

The presence of both acidic and basic adsorption sites on the surface of hydroxyapatite [

{Ca}_{10} {({PO}_{4})}_{6} {(OH)}_{2}

; HAP] is an interesting property for catalytic applications. Here, we report a density functional theory investigation of the adsorption properties of

CO, {CO}_{2}, C_{2} H_{2}, {CH}_{4}, H_{2}, H_{2} O, {NH}_{3}, {SO}_{2}

, and

{BCl}_{3}

on the

HAP (0001)

surface. All probe molecules have a lower energy when they are adsorbed in the region between the most exposed

{Ca}^{2 +}

ion (electron acceptor) and a neighboring

PO {_{4}}^{3 -}

group, where the

O

atoms (electron donor) contribute to the stabilization of the adsorbed molecule. By evaluating the redistribution of the electron density and the change of the atomic charges, the

{Ca}^{2 +}

and

PO {_{4}}^{3 -}

sites were identified as Lewis acidic and Lewis basic adsorption sites, respectively, which indicates that simultaneous acid-base interactions occur upon adsorption of all studied probe molecules. All adsorbates interact with the surface via atoms of opposing charges, which enhances the ionic character of molecular bonds by increasing the distinction between cationic and anionic charges within the molecule. Furthermore, molecules with greater ionic character show stronger interaction with the substrate and greater geometric deformation. Although most adsorbed molecules (

CO, {CO}_{2}, C_{2} H_{2}, {CH}_{4}, H_{2}, H_{2} O

, and

{NH}_{3}

) do not show substantial net charge transfer, polarization effects due to the redistribution of charge are observed upon adsorption of all probe molecules. The change in the work function increases linearly with the total change in the surface dipole moment for

H_{2} O, {NH}_{3}, {SO}_{2}

, and

{BCl}_{3}

, while for the remaining systems, the magnitude of the work function change remains more uniform. By identifying the type of interaction between each probe molecule and the

HAP (0001)

surface, the present study contributes to the understanding of the acid-base properties of the

HAP (0001)

surface, which we elaborated in a short discussion based on the individual bond orders for the acidic and basic sites.

中文翻译：

羟基磷灰石（0001）通过吸附探针分子的酸碱性质：Anab initioInvestigation

羟基磷灰石表面同时存在酸性和碱性吸附位[

钙_{10} {({采购订单}_{4})}_{6} {(哦)}_{2}

; HAP] 是催化应用的一个有趣特性。在这里，我们报告了对吸附性能的密度泛函理论研究

二氧化碳, {二氧化碳}_{2}, C_{2} H_{2}, {CH}_{4}, H_{2}, H_{2} 哦, {NH}_{3}, {所以}_{2}

，和

{氯化硼}_{3}

在

HAP (0001)

表面。当所有探针分子吸附在暴露最多的区域之间时，它们的能量较低。

钙^{2 +}

离子（电子受体）和相邻的

采购订单 {_{4}}^{3 -}

组，其中

哦

原子（电子供体）有助于吸附分子的稳定。通过评估电子密度的重新分布和原子电荷的变化，

钙^{2 +}

和

采购订单 {_{4}}^{3 -}

位点分别被确定为路易斯酸性和路易斯碱性吸附位点，这表明在吸附所有研究的探针分子时同时发生酸碱相互作用。所有被吸附物都通过相反电荷的原子与表面相互作用，这通过增加分子内阳离子和阴离子电荷之间的区别来增强分子键的离子特性。此外，具有更大离子特性的分子显示出与基材的更强相互作用和更大的几何变形。尽管大多数吸附分子（