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<p>In this work Debye–Waller factors (DWF) and extended X-ray absorption fine structure (EXAFS) of bcc crystals have been studied based on the advanced anharmonic correlated Einstein model (AACEM). The many-body effect is included in all considered quantities based on a derived anharmonic effective potential including the first shell near-neighbor contributions to the vibrations between absorber and backscatter atoms. The Morse potential is assumed to describe the single-pair atomic interaction. The analytical expressions of temperature-dependent anharmonic DWFs presented in terms of cumulant expansion approach and thermal expansion coefficient have been derived based on quantum thermodynamic perturbation theory. The important advances in the AACEM are performed by calculating the anharmonic contribution to the second cumulant and the application of this AACEM to EXAFS creating an effective method for the accurate structural determination. The numerical results of Mo (bcc) agree well with the experimental values.</p>

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Debye–Waller factors and EXAFS of bcc crystals based on advanced anharmonic correlated Einstein model

  • 期刊论文

  • 发表日期：

    2026年2月5日

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  • Nguyen Van Hung,
  • Nguyen Cong Toan

摘要

In this work Debye–Waller factors (DWF) and extended X-ray absorption fine structure (EXAFS) of bcc crystals have been studied based on the advanced anharmonic correlated Einstein model (AACEM). The many-body effect is included in all considered quantities based on a derived anharmonic effective potential including the first shell near-neighbor contributions to the vibrations between absorber and backscatter atoms. The Morse potential is assumed to describe the single-pair atomic interaction. The analytical expressions of temperature-dependent anharmonic DWFs presented in terms of cumulant expansion approach and thermal expansion coefficient have been derived based on quantum thermodynamic perturbation theory. The important advances in the AACEM are performed by calculating the anharmonic contribution to the second cumulant and the application of this AACEM to EXAFS creating an effective method for the accurate structural determination. The numerical results of Mo (bcc) agree well with the experimental values.