以第一性原理研究CaCO_3的表面能与电子结构  

Surface Energy and Electronic Structure of CaCO_3 from First-principles Study

作　　者：吴东海[1] 童张法[1,2] 罗涛朋 邵琳 王海晨 韦柳婷[1] 唐壁玉[1] 

机构地区：[1]广西大学化学化工学院,广西南宁530004 [2]广西碳酸钙产业化工程院,广西南宁530004

出　　处：《材料科学与工程学报》2015年第6期857-861 809,共6页Journal of Materials Science and Engineering

摘　　要：采用第一性原理方法和slab模型研究了方解石型CaCO3(10~10)和(0001)晶面的表面能、表面驰豫与电子结构。结果表明(0001)面因较高的表面能而更不稳定,易与其它物质反应且具有较快的生长速度。(10-10)晶面因表面能低而生长缓慢,容易暴露。弛豫后(10-10)表面的Ca、C原子向内收缩而O原子却略微向外扩张,CO2-3集团发生转动使结构更稳定。(0001)表面的Ca原子以及第二层的C、O原子均向内收缩并且原子弛豫程度比(10-10)面大。计算的DOS表明:与CaCO3体相约5.0eV的带隙相比,表面结构的带隙略微减少,而(0001)表面减少更多。虽然表面C原子与O原子由于强烈的DOS交叠形成典型的共价键,而Ca-O键则相对较弱,(0001)表面结构的C-O和Ca-O键相对更弱,且表面稳定性主要与O-p电子有关。电荷密度表明(0001)面内的C原子与周围3个O原子之间存在强烈的C-O共价键而组成三角形状的CO2-3集团,其键能远大于Ca-O键。(10-10)表面模型的CO和Ca-O键均比(0001)面强,并且表面的电荷密度也高于(0001)面,因而更稳定。Surface energy,surface relaxation and electronic structure of(10-10)and(0001)surface for calcite CaCO3 were systematically studied using first-principles calculations with slab-model. Results demonstrate that(0001)surface has higher surface energy,thus less stable and grows faster than(10-10)surface which is thus easy to be exposed due to lower surface energy.After surface relaxation,Ca and C atoms in(10-10)surface contract inwards while O atoms expand outwards slightly.Rotation of surface CO2-3 groups results in more stable structure.Ca,C and O atoms of(0001)surface contract inwards and relaxation degree is higher than that of(10-10)surface.DOS indicates that bulk CaCO3 has a band-gap of about 5.0eV,while band-gap of surface structure narrows and(0001)surface has the narrowest band-gap value.C-O bonding is stronger than Ca-O bonding,both C-O and Ca-O bondings in(0001)surface are relatively weak.Surface stability is closely related to O-p electrons.Charge density shows that three C-O bondings in(0001)plane form triangular CO2-3 group.C-O and Ca-O bondings in(10-10)surface are stronger than that in(0001)surface,and charge density of(10~10)surface is also higher,thus(10-10)surface is more stable.

关 键 词：CACO3 表面能 表面驰豫 电子结构 第一性原理 

分 类 号：TQ132.32[化学工程—无机化工]