KDP晶体本征中性点缺陷的第一性研究

Research on the neutral native point defects in KDP crystals using first-principles theory

用第一性原理研究了KH2PO4(KDP)晶体中性本征点缺陷的形成能并计算了常温下点缺陷的浓度。计算得到中性填隙氢原子的形成能为2.05 eV,进而得到298 K下的浓度约为1.21×10-17mol/L。由于填隙氢原子在带隙中形成缺陷能级,并使能隙降低了2.6 eV,因此消除填隙氢原子有利于提高晶体在355 nm附近的激光损伤阈值。计算得到的氧间隙、氧空位、钾空位和氢空位的形成能分别为0.60、5.25、6.50和6.58eV,常温下它们在晶体中也以较高的浓度存在。钾空位使晶胞体积增大约3.2%,并可能提高晶体电导率,从而降低光损伤阈值。P取代K的反位结构缺陷形成能尽管较低(4.1 eV),但由于晶体生长溶液中P是以PO4四面体的形式存在,故此点缺陷的存在几率很小。

The formation energies and concentrations at room temperature of various neutral native point defects in KDP crystals were studied using first-principles theory. The calculation results show that Hi may be the dominant point defect at room temperature in KDP. The formation energy of O vacancy （5.25 eV） is much higher than that of O interstitial （0.60 eV）. Optical absorption center may be formed due to the O vacancy and may be responsible for the lowering of the damage threshold in KDP. K vacancy enlarges the volume of cavity surrounded by the eight O atoms by about 3.20%. K-vacacy（VK ） defect may increase ionic conductivity and therefore laser-induced damage threshold decrease.