RAMAN FREQUENCY SHIFTS AND THE UODE GRONEISEN PARAMETER FOR THE TO MODE OF NH Cl NEAR PHASE TRANSITIONS

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1993

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Ohio State University

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Raman frequency shifts for the $(144 cm^{-1})$ TO mode of $NH_{4}C1$ have been calculated at various temperatures for zero pressure near phase transitions $(P=O,T = 241.5 K)$ in this crystal system.By defining the mode Gr\""{u}neisen parameter at cons\""{a}nt pressure as , we have obtained $\nu= 2.1293$ for the 144 cm Raman mode across phase traHsition region using our observed Raman frequency data for this mode and the length-change data of $NH_{4}Cl$ from the literature. Using this constant * value, we have calculated the Raman frequencies for the $\nu_{5}(144cm^{-1})$ TO mode.Comparson between our calculated and observed values for this Raman mode in $NH_{4}CI$ gives good agreement.

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Author Institution: Department of Physics, Istanbul Tecnnical University

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