High-order anharmonic effective potentials and four EXAFS cumulants have been studied taking into account the influence of the nearest neighbors of absorbing and backscattering atoms by Analytical expressions of th quantum potential expanded in the fourth order which influences from the 4thcumulants. Numerical results for Ni are found to be in good a experiment and the classical theory. | March 2018|Số 07– Tháng 3 năm 2018| TẠP CHÍ KHOA HỌC ĐẠI HỌC TÂN TRÀO ISSN: 2354 - 1431 High – order anharmonic effective potentials and EXAFS cumulants of Nickel crystal by quantum perturbation theory Tong Sy Tiena*; Nguyen Tho Tuanb;Nguyen Van Namb a University of fire fighting & prevention Hong Duc University * Email: tongsytien@ b Article info Abstract Recieved: 15/01/2018 Accepted: 10/3/2018 High-order order anharmonic effective potentials and four EXAFS cumulants have been studied taking into account the influence of the nearest neighbors of absorbing and backscattering atoms by the anharmonic correlated Einstein model model. Analytical expressions of these th quantities have calculated based on the quantum quantum-statistical perturbation theory derived from a Morse interaction potential expanded in the fourth order which influences from the 2ndto the 4thcumulants. Numerical results for Ni are found to be in good aagreement with experiment and the classical theory. theory Keywords : EXAFS cumulants; quantum perturbation theory;Nickel crystals. 1. Introduction Extended X-ray ray Absorption Fine Structure (EXAFS) has been developed into apowerful technique for providing information on the local atomic structure and thermodynamic parameters of the substances [5, 6]. At anyy temperature the position of the atoms and interatomic distances are changed by thermal vibrations. For a two-atomic atomic molecule, the EXAFS cumulants can be expressed as a function of the force constant of the one-dimensional one interaction bare potential [1, 4]. ]. For many-atomic many systems, like crystals, the EXAFS cumulants are often connected to the force constants of a oneone dimensional effective pair potential using the same relation as for a two-atomic atomic molecule. However, the connection between EXAFS cumulants and an physical properties of many-atomic atomic systems is still a matter mat of debate,
