无机-有机杂化非线性光学晶体材料LAP和d-LAP晶体红外吸收边计算

根据双原子谐振子模型近似,提出了估算分子晶体材料红外吸收边的理论方法,然后利用超分子量子化学从头算,计算了L-精氨酸一水磷酸盐(LAP)晶体和氘化L-精氨酸一水磷酸盐(d-LAP)晶体单元超分子的红外振动光谱,其中LAP晶体超分子计算值与晶体红外光谱实验值吻合,表明超分子计算能有效地模拟无机-有机杂化非线性光学晶体的红外振动光谱。在归属了超分子重要基频线后,分析其红外强度,并估算了泛频频率。根据我们提出的方法,估算了这两种晶体的红外吸收边,结果与实验值较吻合。表明我们建议的理论方法是合理的。此外,通过计算表明,如果非线性光学晶体材料的红外吸收边是由与活泼H有关的伸缩振动泛频频率决定,那么活泼H的氘化是一种改善红外吸收边的有效途径。

Calculations of the IR Absorption Edges of Two Inorganic-Organic NLO Crystals, L-Arginine Phosphate Monohydrate (LAP) and Its Deuterated Analog (d-LAP)

In the present paper a theoretical method has been suggested in order to predicate the IR absorption edges of two inorganic-organic NLO crystals, L-Arginine Phosphate Monohydrate (LAP) and its deuterated analog (d-LAP). We first calculated and simulated the IR spectra of LAP and d-LAP crystals by using ab initio calculations of supermolecular models, of which the former agreed well with the experimental values. It is exhibited that quantum chemical calculations can successfully predicate the IR spectra of these crystals. Subsequently, the important fundamental lines have been assigned and the IR intensities and overtones of these fundamentals have been analyzed. Finally, the IR absorption edges of LAP and d-LAP crystals have been estimated according to the method suggested by us, and the calculated values are very close to the experimental ones. In addition, it is shown that if the IR absorption edges of the crystals are determined by the overtone frequency correlated to H stretching, the deuterated method of H is very effective in improving the ranges of optical transparency.