Origin of antiferroelectricity in NH4H2PO4 from first principles
Origin of antiferroelectricity in NH4H2PO4 from first principles
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DOI：
10.1103/physrevlett.98.267601
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发表时间：
2007-06-29
影响因子：
8.6
通讯作者：
Migoni, R. L.
中科院分区：
文献类型：
--
作者：
Lasave, J.;Koval, S.;Migoni, R. L.
NH_4H_2PO_4的低温反铁电(AFE)相对应于O-H-O桥中的H有序，导致H_2PO_4基团极化垂直于四方c轴，并在链中交替。我们在密度泛函理论的框架下，通过第一性原理计算确定了这种有序的微观起源。具有相关电荷转移和NH4+基团扭曲的N-H中心点O桥的形成对于稳定AFE构型以对抗c极化的铁电(FE)相以及其他垂直于c轴极化的FE态是必不可少的。这些FE态仅位于AFE相上方几meV处，这解释了在AFE相变附近观察到FE和AFE相共存的现象。
The low-temperature antiferroelectric (AFE) phase of NH4H2PO4 corresponds to H ordering in O-H-O bridges leading to H2PO4 group polarizations perpendicular to the tetragonal c axis and alternating in chains. We determine the microscopic origin of such order by means of first-principles calculations in the framework of the density functional theory. The formation of N-H center dot center dot center dot O bridges with correlated charge transfers and NH4+ group distortions turn out to be essential in stabilizing the AFE configuration against a c-polarized ferroelectric (FE) phase, as well as other FE states polarized perpendicular to the c axis. These FE states lie only a few meV above the AFE phase, which explains the observation of FE-AFE phase coexistence near the AFE transition.