Lattice Dynamics of (ND4Br)x(KBr)1-x Mixed Crystals

Authors: Alpana Tiwari, N. K. Gaur

Abstract:

We have incorporated the translational rotational (TR) coupling effects in the framework of three body force shell model (TSM) to develop an extended TSM (ETSM). The dynamical matrix of ETSM has been applied to compute the phonon frequencies of orientationally disordered mixed crystal (ND4Br)x(KBr)1-x in (q00), (qq0) and (qqq) symmetry directions for compositions 0.10≤x≤0.50 at T=300K.These frequencies are plotted as a function of wave vector k. An unusual acoustic mode softening is found along symmetry directions (q00) and (qq0) as a result of translation-rotation coupling.

Keywords: Orientational glass, phonons, TR-coupling.

Digital Object Identifier (DOI): doi.org/10.5281/zenodo.1111837

References:

[1] I. Fehst et.al., Phys. Rev. Lett. vol.64 (1990) 3139.
[2] Hochli U.T., Knorr K. and Loidl A., Adv. Phys. vol.39 (1990) 405.
[3] A. Heidemann, J. Howard, K. J. Lushington, J. A. Morrison, W. Press and J. Tomkinson J. Phys. Soc. Jpn. vol.52 (1983) 2401-2413.
[4] C.Bostoen, G.Coddens and W.Wegener, Physica B, vol 156&157 (1989)350-352; J. Chem. Phys. 91, 10 (1989) 6337-6344.
[5] J.F.Berret,J.L.Sauvajol and S.Haussühl, J.Chem.Phys. vol 96(7)(1992)4896.
[6] R.Mukhopadhyay, J. Tomkinson and C.J.Carlile, Europhys.Lett. vol 17 (1992)201.
[7] R.Mukhopadhyay, J. Tomkinson and C.J.Carlile, Physica B vol 202 (1994) 287.
[8] M. Ohl,F.Guthoff and A.Loidl, Physica B vol 234-236 (1994) 412.
[9] S.Kamba, J.Petzelt, J.Pokorny and A.Loidl, Physica B vol 244 (1998) 172.
[10] F.Guthoff ,M. Ohl, M.Reehuis and A.Loidl, Physica B vol 266 (1999) 310.
[11] F.Matallana, A.Garcia and R.A.Vergas, Phys.Stat.Sol. (b) vol 220 (2000) 655.
[12] M. Ohl,F.Mayr M.Reehuis,W.Schmidt and A.Loidl, Physica B vol 276 (2000) 471.
[13] M. Ohl,F.Mayr M.Reehuis,W.Schmidt and A.Loidl, J. Phys. Condensed. Matter vol 13 (2001) 10221.
[14] J.F.Berret,C.Bostoen & B.Hennian, Phys. Rev. B vol 46 (1992)13747. 7.
[15] R.K. Singh and N.K. Gaur, Z. Phys. vol B75 (1989) 127.
[16] Alpana Tiwari, N. K. Gaur and R.K.Singh, Phys. Stat. Sol.B vol 246 (2009)1215.
[17] Alpana Tiwari, N. K. Gaur and R.K.Singh, J. Phys. Chem. Solids vol 71,717-721(2010).
[18] Alpana Tiwari and N. K. Gaur, AIP Conf. Proc. vol 1349, (2011) 843- 844.
[19] Alpana Tiwari, N.K.Gaur and Preeti Singh, J. Phys. Conference series, vol 215 (2010)012062.
[20] P. Singh, N.K Gaur, Phys. Lett. vol A371 (2007)349.
[21] R.K. Singh and N.K. Gaur, Z. Phys. vol B75 (1989) 127.
[22] R. K. Singh, Phys. Reports, vol 85 (1982) 259.
[23] M.P. Tosi and F.G. Fumi, J. Phys. Chem. Solids 23, (1962)356; M.P. Tosi, Sol. State Phys. vol 2, (1964) 1.
[24] D.W. Hafemeister and W.H. Flygare, J. Chem. Phys. vol 43 (1965) 795.
[25] L. Pauling, Z. Crystallogr. vol 67 (1928) 377.
[26] S.D. Mahanti and D. Sahu, Phys. Rev. Lett. vol 48, (1982)936.
[27] D. Sahu and S.D. Mahanti, Phys. Rev. B vol 29, (1984)340.
[28] D. Strauch, U. Schroder and M. Bauernfeind, Sol. Stat. Com. vol 30, 559 (1979).
[29] W. Cochran, CRC Rev. Sol. State Sc. vol 2, (1971) 1.
[30] Vegards L, Z. Phys. vol 5 (1921) 17.
[31] J.F.Berret, J.L.Sauvajol and B. Hennion, J.Phy. Condensed. Matter vol 4, 9235 (1992).
[32] K. Knorr, Phys. Rev. Lett. vol 63 (1989) 2749.