Correlated and Uncorrelated Debye-Waller Factors and Correlation Function in Atomic Vibrations Including Many-Body Effects

N. Van Hung, N. Cong Toan Department of Physics, VNU University of Science, 334 Nguyen Trai, Thanh Xuan, Hanoi, Vietnam

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Correlated and uncorrelated Debye-Waller factors and correlation function in atomic vibrations described by mean square relative displacement, mean square displacement, and displacement-displacement correlation function, respectively, have been studied based on correlated and uncorrelated Einstein models, including many-body effects. The impact of many-body effects in the derived analytical expressions of the above-considered quantities is realized by using the effective potentials of the derived Einstein models, which take into account the contributions of all nearest neighbors of vibrating atoms. The Morse potential is used to describe the single-pair atomic interactions. The difference between the correlated Debye-Waller factor and the uncorrelated one is considered to be the source of the correlation effect described by the correlation function, which is temperature- and crystal-type-dependent. The larger such difference is, the stronger the correlation effect it generates. The numerical results for the Cu crystal agree with experimental results and with those calculated using other theories.

DOI:10.12693/APhysPolA.146.95 topics: correlated and uncorrelated Debye-Waller factors, correlation function, correlated and uncorrelated Einstein models, effective potentials and many-body effects