HfV2·Hx中扩散导致的1H核自旋弛豫 近邻无规行步处理

对氢合金HfV₂·H_x中¹H核自旋弛豫起主导的因素是偶极相互作用,研究的核心是如何理论计算¹H在基质晶格中扩散造成偶极相互作用涨落的谱密度。我们把Torrey同核偶极作用近邻无规扩散行步理论推广到同核、异核偶极作用并存的情况;并就中子衍射提供的HfV₂·H_x结构(C-15)参数计算了确定谱密度J_q^HH(ω)和J_q^HV(ω)(q=0,1,2)所需的G_HH(k,y)和G_HV(k,y)。引用以前别人的核磁共振实验数据,依照我们的理论分析计算扩散激活能和H在间隙位上的振动频率;与他们用唯象理论获得的相应数值对比,结果是满意的。 关键词：

1H NUCLEAR SPIN RELAXATION CAUSED BY DIFFUSION IN HfV2·Hx THE MODEL OF RANDOM WALK TO NEAREST NEIGHBOR SITES

The dominent factors affecting the nuclear spin relaxation of ¹H in HfV₂·H_x hydrides are dipolar couplings. The important theoretical problem is the calculation of spectral density functions for the fluctuation of the dipolar couplings caused by the diffusive motion of 1H in the host lattice. We extended Torrey's theory, based on the model of random walk to nearest neighbor sites for homonuclear dipolar interaction, to the case that both homo- and heteronuclear interactions are existent. Then we calculated the G_HH(k, y) and G_HV(k, y) for determining the spectral densities J_q^HH(ω) and J_q^HV(ω) (q = 0, 1,2) according to the structure constants and H occupations of HfV₂ ·H_x obtained from neutron diffractions. Using our theory and data derived from previous work of others, we analyzed the activation energy and the attempt frequency of ¹H on interstitial sites and found that our results are satisfactory as compared with the conclusion derived from the phenomenological theory.