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  • Article


  • Authors: Nguyen, Van Hung; Tran, Trung Dung; Nguyen, Cong Toan (2004)

  • A new procedure for description and calculation of the interaction potential and force constants for fee crystals containing an arbitrary number n of impurity atoms have been developed. Analytical expressions for the effective atomic interaction potential, the single-bond and effective spring constants have been derived. They depend on the number of the impurity atoms and approach those derived by using anharmonic correlated Einstein model, if all the impurity atoms are taken out or they replace all the host atoms. Numerical results for Ni doped by Cu atoms show significant changes of the interact on potential and spring constants of the substance if the number of impurity atoms is changed.

  • Article


  • Authors: Nguyen, Van Hung; Ho, Khac Hieu; Nguyen, Cong Toan (2006)

  • A new procedure for calculation and analysis of thermodynamic and correlation effects of bcc crystals under in fluence of dopant atom in the X-ray Absorption Fine Structure (XAFS) has been developed. Analytical expression for the Displacement-displacement Correlation Function (DCF) CR has been derived based on the derived Mean Square Relative Displacement (MSRD) 2 Ơ2 and Mean Square Displacement (MSD) u of bcc crystals containing dopant atom. Numerical calculations have been carried out for Fe doped by w and by Cr atom. They are found to be in good agreement with experiment.

  • Article


  • Authors: Nguyen, Van Hung; Tran, Trung Dung; Nguyen, Cong Toan (2006)

  • A new procedure for description and calculation of th EXAFS (Extended X-ray Absorption Fine Structure) cumulants for fee crystals containing an abitrary number n of dopant atoms have been developed. Analytical expressions for the l 8t, 2nd and 3rd cumulants have been derived.They depend on the number of dopant atoms and approach those derived by anharmonic correlated Einstein model, if all dopant atoms are taken out or replacing all the host atoms. Numerical results for Cu doped by Ni atoms based on the Morse potential show significant dependence of thermodynamic parameters of the substance on the number of dopant atoms and a reasonable agreement with experiment.

  • Article


  • Authors: Nguyen, Van Hung; Le, Thi Thuy Hau; Tong, Sy Tien (2007)

  • A new procedure for calculation and analysis of XAFS (X-ray Absorption Fine Structure) cumulants of hep crystals containing dopant atom has been derived based on quantum statistical theory with generalized anharmonic correlated Einstein model. Analytical expressions for effective local force constants, correlated Einstein frequency and temperature, first cumulant or net thermal expansion, second cumulant or Debye Waller factor and third cumulant of hep crystals containing dopant atom have been derived. Morse potential parameters of pure crystals and those with dopant included in the derived expressions have been calculated. Numerical results for Zn doped by Cd are found to be in good agreement with experiment.

  • Article


  • Authors: Nguyen, Van Hung; Nguyen, Bao Trung (2006)

  • An anharmonic correlated Debye model has been derived for vibrational amplitudes in the X-ray Absorption Fine Structure (XAFS). The model includes anharmonic effects based on Morse potential parameters. Analytical expression for Debye-Waller factor or second cumulant for different atomic shells has been derived. Numerical results for Cu approach those obtained by the anharmonic Einstein model. Both they contain zero-point contribution at low temperatures and linearly depend on the temperature at high temperatures as the classical limit values. They reflect the experimental results.

  • Article


  • Authors: Bui, Van Loat; Nguyen, Van Hung; Hoang, Sy Minh Phuong (2010)

  • At present, thickness measurement of materials based on effect of backscattering gamma-ray has been widely used in industry in our country. The report presented research in measuring thickness of some materials such as paper, plastic, aluminum and steel with using the dedicated system of MYO-101, having scintillation detector of YAP(Ce) and gamma-ray of 60 keV of Am-241 source, by Monte-Carlo simulation using the code of MCNP. The simulation was checked by experimental measurements. The results were shown that they were in accordance with the range of error. This research has been useful for training activities with a view of human resowces development in the field of application of nuclear techni.que in industry in Vietnam.

  • Article


  • Authors: Khong, Cat Cuong; Trinh, Duc Thien; Pham, Thu Nga; Nguyen, Van Minh; Nguyen, Van Hung (2009)

  • In this article, we report on the preparation of CdSe quantum dots (QDs) by sol-gel method and their optical properties. The average size of QDs is also estimated by using various ways, such as the Scherer’s formula. The Effros-Brus-Kayanum a's theoretical expression, TEM etc. The TEM images of samples show that the mean sizes of QDs are 4 nm. The mean sizes of QDs are smaller than that of other methods and arranging from 2 to 3.6 nm.

  • Article


  • Authors: Nguyen, Van Hung (2003)

  • An analytical method for calculation and evaluation of thermodynamic properties of alkali metals under the influence of impurity atom has been developed based on quantum statistical theory with correlated Einstein model. Mean square relative displacement (MSRD), effective local force constants, correlated Einstein frequency and temperature of pure alkali metals and those with impurity have been calculated and compared each to other.

  • Article


  • Authors: Nguyen, Van Hung; Dao, Xuan Viet (2003)

  • A new procedure for calculation of the Morse potential parameters of hexagonal closed packed (hcp) crystals has been developed using the energy of sublimation, the compressibility and the lattice constant. The derived equation of state and the elastic constants computed using the obtained Morse parameters agree with the experimental ones. This shows that the Morse dunction can be applied validly to the problems involving any type of deformation and atomic interaction in the hcp crystals.