The positron lifetimes of some compounds with NaCl-type crystal structure are calculated with the method of atomic superposition approximation （ATSUP） based on the theories of local-density-approximation （LDA） and...The positron lifetimes of some compounds with NaCl-type crystal structure are calculated with the method of atomic superposition approximation （ATSUP） based on the theories of local-density-approximation （LDA） and general- gradient-approximation （GGA）. The systematical results are fitted to a curve as a function of lattice constants. The positron bulk lifetimes of some other compounds with NaCl-type crystal structure, which are deduced from the systematical results, are in agreement with the experimental results given in other literature.展开更多
The band structures of Group IVB (Ti, Zr, Hf), VB (V, Nb, Ta) and VIE (Cr, Mo, W) transition metals and some of their carbides and nitrides (TiN, ZrN, HfN, VC, NbC, TaC, VN, NbN, TaN) with NaCl-type (B1-type) structur...The band structures of Group IVB (Ti, Zr, Hf), VB (V, Nb, Ta) and VIE (Cr, Mo, W) transition metals and some of their carbides and nitrides (TiN, ZrN, HfN, VC, NbC, TaC, VN, NbN, TaN) with NaCl-type (B1-type) structure have been calculated by using the tight-binding method within the Extended Huckel approximation (EHT). The energy bands, densities of states and crystal orbital overlap populations are given. The relationship between the bonding properties and the superconducting transition temperatures (T-c) of them is discussed. The influences of various kinds of metallic atoms and changes of bond lengths on T-c are also discussed.展开更多
棉花是鲁北平原种植的重要经济作物,合理利用微咸水和咸水资源是解决棉花季节干旱问题的重要途径。通过田间小区试验,以淡水滴灌处理为对照,设置不同盐分梯度的咸水滴灌处理,研究2种类型咸水滴灌对棉田土壤水分和盐分的分布影响以及棉...棉花是鲁北平原种植的重要经济作物,合理利用微咸水和咸水资源是解决棉花季节干旱问题的重要途径。通过田间小区试验,以淡水滴灌处理为对照,设置不同盐分梯度的咸水滴灌处理,研究2种类型咸水滴灌对棉田土壤水分和盐分的分布影响以及棉花产量的响应。结果表明,咸水滴灌条件下主要影响棉田40~100 cm土壤水分的变化,碳酸氢钠型和氯化钠型咸水处理对土壤含水量的影响没有显著差异。利用EC值低于8 d S·m^(-1)的咸水进行补灌,棉田0~40 cm土壤盐分积累不明显,灌溉水EC值为10 d S·m^(-1)的氯化钠型咸水灌溉在0~100 cm土壤盐分有明显的积累。滴灌补灌EC值不大于6 d S·m^(-1)的碳酸氢钠型咸水和不大于8 d S·m^(-1)的氯化钠型咸水对棉花产量没有明显的影响,滴灌补灌7 d S·m^(-1)碳酸氢钠型和10 d S·m^(-1)氯化钠型咸水明显降低棉花产量。从土壤盐分的积累和棉花产量来看,在鲁北平原可以利用6 d S·m^(-1)咸水滴灌对棉花进行补灌;利用咸水滴灌,要同时考虑灌溉水盐分的数量和盐分组成,碳酸氢钠型咸水要更加谨慎利用。展开更多
本文对二维氯化钠型结构的马德隆常数进行求算。首先确定其无穷级数的具体形式,为: 4-1/2^(1/2)-4/2+8/5^(1/2)-4/8^(1/2)+…并将其整理成通式: 4 sum from k=1 to π (-1)^(k=1) 1/k-4/2^(1/2) sum form =1 to π 1/k+8 sum from =2 to...本文对二维氯化钠型结构的马德隆常数进行求算。首先确定其无穷级数的具体形式,为: 4-1/2^(1/2)-4/2+8/5^(1/2)-4/8^(1/2)+…并将其整理成通式: 4 sum from k=1 to π (-1)^(k=1) 1/k-4/2^(1/2) sum form =1 to π 1/k+8 sum from =2 to π sum from I=1 to k=1 (-1)^(+I-1) 1/(K^2+I^2)^(1/2) 然后分别求算通式中每一项的收敛值。这些收敛值之和为1.6152,此即二维氯化钠型结构的马德隆常数。展开更多
基金supported by the National Natural Science Foundation of China (Grant Nos. 10675114 and 10835006)the Important Direction Project of the Chinese Academy of Sciences
文摘The positron lifetimes of some compounds with NaCl-type crystal structure are calculated with the method of atomic superposition approximation （ATSUP） based on the theories of local-density-approximation （LDA） and general- gradient-approximation （GGA）. The systematical results are fitted to a curve as a function of lattice constants. The positron bulk lifetimes of some other compounds with NaCl-type crystal structure, which are deduced from the systematical results, are in agreement with the experimental results given in other literature.
基金Project supported by the National Natural Science Foundation of China and the Foundation of the State Key Laboratory of Structural Chemistry of China.
文摘The band structures of Group IVB (Ti, Zr, Hf), VB (V, Nb, Ta) and VIE (Cr, Mo, W) transition metals and some of their carbides and nitrides (TiN, ZrN, HfN, VC, NbC, TaC, VN, NbN, TaN) with NaCl-type (B1-type) structure have been calculated by using the tight-binding method within the Extended Huckel approximation (EHT). The energy bands, densities of states and crystal orbital overlap populations are given. The relationship between the bonding properties and the superconducting transition temperatures (T-c) of them is discussed. The influences of various kinds of metallic atoms and changes of bond lengths on T-c are also discussed.
文摘棉花是鲁北平原种植的重要经济作物,合理利用微咸水和咸水资源是解决棉花季节干旱问题的重要途径。通过田间小区试验,以淡水滴灌处理为对照,设置不同盐分梯度的咸水滴灌处理,研究2种类型咸水滴灌对棉田土壤水分和盐分的分布影响以及棉花产量的响应。结果表明,咸水滴灌条件下主要影响棉田40~100 cm土壤水分的变化,碳酸氢钠型和氯化钠型咸水处理对土壤含水量的影响没有显著差异。利用EC值低于8 d S·m^(-1)的咸水进行补灌,棉田0~40 cm土壤盐分积累不明显,灌溉水EC值为10 d S·m^(-1)的氯化钠型咸水灌溉在0~100 cm土壤盐分有明显的积累。滴灌补灌EC值不大于6 d S·m^(-1)的碳酸氢钠型咸水和不大于8 d S·m^(-1)的氯化钠型咸水对棉花产量没有明显的影响,滴灌补灌7 d S·m^(-1)碳酸氢钠型和10 d S·m^(-1)氯化钠型咸水明显降低棉花产量。从土壤盐分的积累和棉花产量来看,在鲁北平原可以利用6 d S·m^(-1)咸水滴灌对棉花进行补灌;利用咸水滴灌,要同时考虑灌溉水盐分的数量和盐分组成,碳酸氢钠型咸水要更加谨慎利用。
文摘本文对二维氯化钠型结构的马德隆常数进行求算。首先确定其无穷级数的具体形式,为: 4-1/2^(1/2)-4/2+8/5^(1/2)-4/8^(1/2)+…并将其整理成通式: 4 sum from k=1 to π (-1)^(k=1) 1/k-4/2^(1/2) sum form =1 to π 1/k+8 sum from =2 to π sum from I=1 to k=1 (-1)^(+I-1) 1/(K^2+I^2)^(1/2) 然后分别求算通式中每一项的收敛值。这些收敛值之和为1.6152,此即二维氯化钠型结构的马德隆常数。
