亚汞氢氧化物Hg_2(OH)_2结构的理论研究

Theoretical Studies on the Structure of Hg(I)-hydroxidic Compounds

采用从头计算HF ,MP2方法和密度泛函方法 ,选择LanL2DZ和SDD基组 ,对Hg2 (OH) 2 的几何构型、振动频率和稳定性进行了研究 ,并与Hg2 F2 和Hg2 Cl2 的稳定性进行了对比 .研究表明Hg的 5s ,5p准内层电子参与了Hg与Hg之间的成键作用 ,Hg—Hg键强烈的电子相关作用使得HF方法不适用于该体系的研究 .Becke的离域校正给出较大的Hg—Hg键长 ,而局域的DFT方法和MP2方法则给出了合理的结构参数、振动频率和能量 .相对论效应使Hg—Hg键缩短 2 4pm ,增加Hg—Hg键的强度达 2 0 %左右 .Hg2 (OH) 2 的稳定性与Hg2 F2 和Hg2 Cl2 的稳定性相当 .虽然在气相中Hg2 L2 (L =F ,Cl,OH)比其分解物HgL2 和Hg要稳定 ,但相对论效应降低了这种趋势 .

Geometries, vibrational frequencies and stability of Hg 2(OH) 2 as well as Hg 2F 2 and Hg 2Cl 2 have been investigated by means of ab initio HF, MP2 and density functional theory methods with LanL2DZ, SDD basis sets. The 5s, 5p semi-core of Hg has significant contribution to Hg—Hg bonding. HF method is not suitable for the [Hg—Hg] 2+ system due to the strong correlation effects. The non-local exchange correction of Becke functional gives too long Hg—Hg distances. Local spin density functional theory and MP2 may reproduce the spectroscopic constants reasonably. Relativistic effects reduce the Hg—Hg bond lengths by about 24 pm and stabilize the Hg—Hg bond significantly by about 20%. Although Hg 2L 2 (L=OH, F, Cl) in disproportionation reaction Hg 2L 2→HgL+Hg is stable in the gas phase, relativistic effects reduce the tendency. The stability of Hg 2(OH) 2 is comparable to that of mercurous halides.