TAILIEUCHUNG - Báo cáo " Anharmonic effective potential and XAFS cumulants for hcp crystals containing dopant atom "

A new procedure for calculation and analysis of XAFS (X-ray Absorption Fine Structure) cumulants of hcp 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 hcp 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. . | VNU Journal of Science Mathematics - Physics 23 2007 28-34 Anharmonic effective potential and XAFS cumulants for hcp crystals containing dopant atom Nguyen Van Hung Le Thi Thuy Hau Tong Sy Tien Department of Physics College of Science VNU 334 Nguyen Trai Hanoi Vietnam Received 17 June 2007 Abstract. A new procedure for calculation and analysis of XAFS X-ray Absorption Fine Structure cumulants of hcp 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 hcp 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. 1. Introduction To study thermodynamic properties of a substance it is necessary to investigate its effective local force constants correlated Einstein frequency and temperature net thermal expansion mean square relative displacement MSRD or Debye Waller factor and third cumulant 1-14 which are contained in the XAFS 12 . Local force constants of transition metal dopants in a nickel host in XAFS has been investigated but only for comparision to Mossbauer studies 10 . The purpose of this work is to develop a method for calculation and evaluation of the effective local force constants correlated Einstein frequency and temperature first cumulant or net thermal expansion second cumulant or MSRD characterizing Debye Waller factor and third cumulant of hcp crystals containing a dopant D atom as absorber in the XAFS process. Its nearest neighbors are the host H atoms. The derivation is based on the generalization of the anharmonic correlated Einstein model 7 which is .

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