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  • Article


  • Authors: Nguyen, Van Hung; Ngo, Trong Hai; Tong, Sy Tien; Le, Hai Hung (2009)

  • Anharmonic effective potential, effective local force constant, thermal expansion coefficient, three leading cumulants, and EXAFS (Extended X-ray Absorption Fine Structure) of hep crystals have been studied. Analytical expressions for these quantities have been derived. Numerical calculations have been carried out for Zn and Cd. They show a good agreement with experiment results measured at HASYLAB (DESY, Germany) and unnegligible anharmonic effects in the considered quantities.

  • Article


  • Authors: Bui, Van Loat; Nguyen, Van Quan; Le, Tuan Anh; Tran, The Anh; Nguyen, The Nghia; Nguyen, Van Hung (2009)

  • Radioactive sources which used to study were the standardized radioactive of common monoenergetic radionuclide Cs137 and standardized multigamma Co60, Ba133, Eu152. Determination of the absolute efficiency curve and energy resolution as a function of energy of GEM40P4 HPGe spectrometer are presented in this paper.

  • Article


  • Authors: Nguyen, Van Hung; Nguyen, Thi Thu Hoai; Le, Hai Hung (2004)

  • A new procedure for calculation and evaluation of XAFS cumulants of fee crystals containing impurity atom has been developed based on the quantum statistical theory with correlated Einstein model. Analytical expressions for the 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 fee crystals containing impurity atom have been derived. Morse potential parameters of pure crystals and those with impurity included in the derived expressions have been calculated. Numerical results for Cu. Ni. Ni-Cu are found to be in good agreement with experiment

  • Article


  • Authors: Nguyen, Van Hung; Nguyen, Cong Toan; Nguyen, Bao Trung; Ngo, Hoang Giang (2008)

  • Analytical expressions for the Morse potential parameters of diamond crystals have been derived. They contain the energy of sublimation, the compressibility and the lattice constant. Numerical calculations have been carried out for Si and Sn, and the result reflect fundamental calcultion of the anharmonic correlated effective potential parameters have been used for calculation of the anharmonic correlated effective potentials of these crystals in XAFS theory showing clearly anharmonic effects.

  • Article


  • Authors: Nguyen, Van Hung; Bui, Van Loat (2009)

  • The paper resented the results of assessing internal dose for 131I by the direct method for Vietnamese objects that was issued in the Intercomparison Program of IAEA. The results on experimental measurements, caculating intake (I) or 131I to thyroid by the specializing system for measuring thyroid activity, and committed effective dose E(50) using the specializing code of LUDEP 2.0 were shown that the results carrying out at the Nuclear Research Institute were goof and were in accordance with the those of the authors in other laboratories in the world.

  • 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.