Electronic structure calculations of an oxygen vacancy in KH2PO4 -: art. no. 134110
Electronic structure calculations of an oxygen vacancy in KH2PO4 -: art. no. 134110
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KH2PO4 中氧空位的电子结构计算
DOI：
10.1103/physrevb.72.134110
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发表时间：
2005-10-01
影响因子：
3.7
通讯作者：
Radousky, HB
中科院分区：
文献类型：
--
作者：
Liu, CS;Hou, CJ;Radousky, HB
我们提出了 KH{sub 2}PO{sub 4} (KDP) 中氧空位的中性态和电荷态的第一原理全能量密度泛函理论电子结构计算。尽管有缺陷的 KDP 的整体 DOS 分布与完美 KDP 的非常相似，但中性和 +1 电荷态中的氧空位会在带隙中引起缺陷态。对于中性氧空位，间隙态被两个电子占据。总态密度 (DOS) 的积分与投影在 0.98 |e| 原子上的 DOS 之和之间的差异表明，由于氧原子的去除而产生的两个电子之一被捕获在空位中，而另一个则倾向于在相邻原子中离域。对于+1电荷的氧空位，空穴的添加将中性情况下填充的能隙态的占据从两个电子减少到一个电子，并在能隙中产生新的空态。新的空带隙态非常接近最高的占据态，导致带隙急剧减小。总 DOS 的积分与投射在原子上的 DOS 总和之间的差值为 0.56 |e|，这意味着超过 56% 的冗余电子被捕获在氧空位中，44% 的电子分布在邻近的原子上。与此形成鲜明对比的是，+2 电荷 O 空位的能隙中没有出现缺陷态。因此，两个空穴的添加完全补偿了两个冗余电子，并依次消除了中性情况下占据的带隙态。
We present first-principles total-energy density-functional theory electronic structure calculations for the neutral and charge states of an oxygen vacancy in KH{sub 2}PO{sub 4} (KDP). Even though the overall DOS profiles for the defective KDP are quite similar to those of the perfect KDP, the oxygen vacancy in the neutral and +1 charge states induces defect states in the band gap. For the neutral oxygen vacancy, the gap states are occupied by two electrons. The difference between the integral of the total density of states (DOS) and the sum of the DOS projected on the atoms of 0.98 |e|, indicates that one of the two electrons resulting from the removal of the oxygen atom is trapped in the vacancy, while the other tends to delocalize in the neighboring atoms. For the +1 charge oxygen vacancy, the addition of the hole reduces the occupation of the filled gap-states in the neutral case from two to one electron and produces new empty states in the gap. The new empty gap states are very close to the highest occupied states, leading to a dramatic decrease of the band gap. The difference between the integral of the total DOS and the sum of the DOS projected on the atoms is 0.56 |e|, which implies that more than 56% of the redundant electron is trapped in the oxygen vacancy, and 44% spreads over the neighboring atoms. In sharp contrast, no defect states appear in the energy gap for the +2 charge O vacancy. Thus, the addition of the two holes completely compensates the two redundant electrons, and removes in turn the occupied gap states in the neutral case.