Numerical Study of Luttinger Liquid Regime of Two-Leg Hubbard Ladders

We investigate two-leg Hubbard ladders in the Luttinger liquid regime by the density-matrix renormalization group method. Applicability of the bond concept in this region is discussed in a quantitative comparison of power-law decay exponents, energy components and anti-bond occupations between ladders and chains. The interaction between bond and anti-bond bands induced by finite Hubbard repulsion U is emphasized by our numerical results. Our quantitative results are useful for the justification of the validity of various analytical approaches.     

红壤可变电荷矿物的酸碱缓冲能力及表面络合模型

氧化铁和高岭石是红壤中可变电荷的主要来源,对红壤的酸碱变化起到缓冲作用.本研究基于红壤矿物的表征和酸碱滴定实验结果,采用1-site/2-pK表面络合模型获得了其表面活性位点浓度H_s、密度D_s、酸碱平衡常数pK_a^int以及电荷零点pH_pzc等相关参数,定量解析了氧化铁和高岭土的酸碱缓冲能力.结果表明：该模型能较好地适用于分析针铁矿、赤铁矿及高岭石的表面酸碱性质;针铁矿、高岭石表面活性位点浓度H_s较高,说明其对酸具有较好的缓冲效果.根据上述酸碱性质参数,模拟计算了不同pH下的矿物表面化学物种,揭示了矿物表面反应缓冲土壤酸碱变化的机制.采用上述酸碱滴定方法及模型计算方法,分析实际林地红壤样品的酸碱缓冲能力,并采用表面络合模型计算了其表面化学物种,验证了该方法用于林地红壤酸碱缓冲能力分析的可行性.