<span style="font-size:21.0pt;mso-bidi-font-size:14.0pt; line-height:115%;font-family:"Times New Roman","serif";mso-fareast-font-family: "Times New Roman";mso-fareast-theme-font:minor-fareast;mso-ansi-language:EN-US; mso-fareast-language:EN-US;mso-bidi-language:AR-SA">Lattice dynamical studies of ternary superionic conductors Ag_{<span style="font-size:16.0pt; mso-bidi-font-size:9.0pt;line-height:115%;font-family:"Times New Roman","serif"; mso-fareast-font-family:"Times New Roman";mso-fareast-theme-font:minor-fareast; mso-ansi-language:EN-US;mso-fareast-language:EN-US;mso-bidi-language:AR-SA">3</span>}<span style="font-size:21.0pt;mso-bidi-font-size:14.0pt;line-height:115%;font-family: "Times New Roman","serif";mso-fareast-font-family:"Times New Roman";mso-fareast-theme-font: minor-fareast;mso-ansi-language:EN-US;mso-fareast-language:EN-US;mso-bidi-language: AR-SA">SX (X=1, Br)</span></span>

Abstract

<span style="font-size: 15.5pt;mso-bidi-font-size:8.5pt;font-family:" times="" new="" roman","serif""="">A de Launey angular force model has been applied to study the phonon dispersion in three symmetric directions of ternary superionic conductor Ag_{<span style="font-size:13.0pt;mso-bidi-font-size:6.0pt;font-family:" times="" new="" roman","serif""="">3</span>}<span style="font-size:15.5pt;mso-bidi-font-size:8.5pt;font-family:" times="" new="" roman","serif""="">SX (X =1, Br) by assuming them to be ideal perovskite type structure. A lattice dynamical calculation reasonably interprets the dominance of mobile ions in highest frequency mode. The short-range (<i>f_s) </i>and longrange

<i><span style="font-size:15.5pt;mso-bidi-font-size:8.5pt;font-family:" times="" new="" roman","serif""="">(fL) </span></i><span style="font-size:15.5pt;mso-bidi-font-size:8.5pt;font-family: " times="" new="" roman","serif""="">forces in Ag_{<span style="font-size:13.0pt; mso-bidi-font-size:6.0pt;font-family:" times="" new="" roman","serif""="">3</span>}<span style="font-size:15.5pt;mso-bidi-font-size:8.5pt;font-family:" times="" new="" roman","serif""="">SX (X <span style="font-size:19.5pt;mso-bidi-font-size:12.5pt;font-family: " times="" new="" roman","serif""="">=<span style="font-size:15.5pt;mso-bidi-font-size: 8.5pt;font-family:" times="" new="" roman","serif""="">I, Br) for a high frequency band are estimated near the transition temperature <i>T_c </i>and below 300 K. The <i style="mso-bidi-font-style:normal">f_L</i><i><span style="font-size:19.0pt;mso-bidi-font-size:12.0pt;font-family:" times="" new="" roman","serif""=""> </span></i><span style="font-size:15.5pt;mso-bidi-font-size:8.5pt;font-family: " times="" new="" roman","serif""="">values in both the conductors show an increase with <i>T </i>above <i>T_c </i>whereas the values of <i>f_s</i><i><span style="font-size:19.0pt;mso-bidi-font-size:12.0pt;font-family:" times="" new="" roman","serif""=""> </span></i><span style="font-size:15.5pt;mso-bidi-font-size:8.5pt;font-family: " times="" new="" roman","serif""="">decrease with <i>T. </i>The temperature dependence of <i style="mso-bidi-font-style:normal">f_L</i><i><span style="font-size:19.0pt;mso-bidi-font-size:12.0pt;font-family:" times="" new="" roman","serif""=""> </span></i><span style="font-size:15.5pt;mso-bidi-font-size:8.5pt;font-family: " times="" new="" roman","serif""="">and <i>f_s</i><i><span style="font-size:19.0pt;mso-bidi-font-size:12.0pt;font-family:" times="" new="" roman","serif""=""> </span></i><span style="font-size:15.5pt;mso-bidi-font-size:8.5pt;font-family: " times="" new="" roman","serif""="">are explained satisfactorily from this calculation.

</span></span></span></span></span></span></span></span></span></span>