Keywords: 
• NH4H2PO4和ND4D2PO4 /
• 拉曼光谱 /
• 第一性原理 /
• 振动模式

Abstract: In this paper, the lattice vibration modes of ammonium dihydrogen phosphate NH4H2PO4 (ADP) and its deuterated analog DADP are studied by using polarized Raman spectra and the first-principles calculation in the framework of the density functional theory. The vibration modes of ADP crystal, in which the basic structural units are the NH+4 and H2PO?4 groups, have been simulated by using a plane-wave pseudo potential method. Result shows that the peaks of 921 and near 3400 cm?1 are assigned as the vibrational H2PO?4 and NH+4 groups, respectively. In order to investigate the deuteration process, the polarized Raman spectra are obtained in different polarization configurations and recorded in the range of 200–4000 cm?1, so that we can study the variation of Raman peaks at 921 and 2600—3400 cm?1. For example, in the scattering geometry X(Y Y )X, with increasing degree of deuterated, the peak of 921 cm?1 red shifts and decreases in intensity, while the peaks ranging from 2600 to 3000 cm?1 decrease in intensity. Moreover, a new broadened line appears in the range of 2000—2600 cm?1, and the intensity of the new line increases with the degree of deuterated, but no change occurs in the peak position. With Lorentz analysis, it can be inferred that the deuterated of NH+4 group is prior to that of H2PO?4 group. We also study the spectra for other Raman scattering geometry of these crystals, and the result shows that the site symmetries of NH+4 (ND+4 ) and H2PO?4 (D2PO?4 ) groups are determined to be C2, which means that the site symmetry of the two groups in crystals have no change during the deuteration process. These results will be a foundaton for optimizing the growth and property of this kind of material.