of β-Ni(OH) 2 were calculated by quantum chemical DV-Xα method. By analyzing the state densities, orbital populations, net charges and electric charge density differences of the selected clusters, it was indicated that β-Ni(OH) 2 was not typical ionic crystal, and the bonds between Ni and O atoms had obvious covalent characteristics. The bonds between H atom and other atoms in the crystal structure were weaker, which ensured that H atoms can easily deintercalate and intercalate into β-Ni(OH) 2 . The structure of β-Ni(OH) 2 was not changed by moderate de-intercalation of H atoms. However, with the excessive de-intercalation of H atoms, the structure of β-Ni(OH) 2 changed and the electrochemical active properties were reduced. nickel hydroxide, electronic structure, quantum chemistry, DV-Xα methodThe nickel-metal hydride (Ni-MH) battery has many characteristics including high energy density, high-rate discharge capability, longer cycle life, no memory effect, no pollution, being easy to fabricate and safe to handle. In the past years, Ni-MH rechargeable battery has been widely used in many fields and is replacing the traditional nickel-cadmium battery [1,2] . It is well known that the capacity of Ni-MH battery depends on the capacity of the positive electrode according to the principle of the rechargeable battery. For nearly ten years, great progress has been made for the hydrogen storage alloy material as a kind of negative electrode material [3] , however, the progress in positive electrode material of Ni-MH battery lags [4,5] .On the other hand, quantum chemical calculation has become a useful tool for battery design since it can be used to calculate most important properties including open circuit voltage, energy density, structure of phases, instability, conductivity of electrode materials without any requirement of experimentally measured input data. Thereby, experimental investigations can be focused on those materials appearing to be most promising [6] . This paper aims to clarify the cycling mechanics of β-nickel hydroxide (β-Ni(OH) 2 ), as a kind of positive electrode material of Ni-MH battery, by analyzing the electronic structures of Ni 7 O 12 H 12 2+ and Ni 7 O 12 H 9 − atom clusters of β-Ni(OH) 2 from quantum chemical DV-Xα calculation. Calculation models and methodChemically prepared β-Ni(OH) 2 consists of a hexagonal sandwich type (Brucite) structure with a plane of nickel atoms in an array of oxygen atoms (OH). Every crystal cell includes one nickel atom, two oxygen atoms and two hydrogen atoms. The distance a 0 between two nickel atoms is 0.312 nm, and the distance c 0 between two layers is 0.4605 nm [7] (Figure 1(a)). By now, of the popular quantum chemical calculation methods, the discrete variational method (DV-Xα) [8]

Compton scattering saline solution was researched. Firstly according to the Compton scattering theory the linear relationship between the concentration and the scattered photon counts was obtained. And then it was proved by Compton scattering experiments for some solutions. According to those experiments, it was found that the slope was decreased when the atomic number of the cation was increased for alkali metal chloride solutions and alkaline-earth metal chloride solutions. Based on those relationships, a new method was promoted with which to measure the concentration of saline solution untouched the measured solution.

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