Structure and Lattice Expansion of Pure Sodium Confined inside Nanoporous Vycor Glass at Low Temperatures

Abstract:

Behavior of sodium metal subject to geometrical constraints has been studied at variable temperatures. A porous medium, Vycor glass of an average pore size of 9.2 nm, was loaded with Na by vacuum vaporization. Synchrotron X-ray powder diffraction of the specimen revealed the existence of close-packed phases such as FCC, HCP, 9R and 4H already at room temperature whereas the bulk BCC phase of Na was completely absent. In contrast, close-packed phases in bulk sodium are only observed at temperatures below 35 K upon cooling. This result can be qualitatively understood in view of earlier zero Kelvin calculations from which it is well known that the differences of structural energies between BCC and close-packed phases are very small. As a consequence, also various close-packed structures can be formed at ambient temperature under certain conditions and environments. The lattice expansion in the restricted geometry has been determined in the range of 160 K to 300 K and compared with the bulk metal. Confined Na exhibits smaller lattice expansion as compared to that of the bulk which likewise can be explained as being due to confinement.

• Periodical: Applied Mechanics and Materials (Volumes 313-314)
• Pages: 93-97
• DOI: https://doi.org/10.4028/www.scientific.net/AMM.313-314.93
• Online since: March 2013
• Authors: Abdul Ghaffar, Wolfgang Pichl, Gerhard Krexner, Roman Schuster
• Keywords: Confinement Induced Structural Effects, Linear Expansion, Metallic Sodium, Vycor Glass

References

[1] R. Berliner, O. Fajen, H.G. Smith and R.L. Hitterman, Phys. Rev. B Vol. 141 (1989), 12086

[2] A.W. Overhauser, Phys. Rev. Lett. Vol. 53 (1984), 64

[3] O. Blaschko, V. Dmitriev, G. Krexner and P. Tolédano, Phys. Rev. B Vol. 59 (1999), 9095

[4] O. Blaschko and G. Krexner, Phys. Rev. B Vol. 30 (1984), 1667

[5] W. Schwarz, O. Blaschko and I. Gorgas, Phys. Rev. B Vol. 46 (1992), 14448

[6] G. Ernst, C. Artner, O. Blaschko and G. Krexner, Phys. Rev. B Vol. 33 (1986), 6465

[7] K. Knorr, P. Huber and D. Wallacher, Z. Phys. Chem. Vol. 222 (2008), 257

[8] H. Thompson, A.K. Soper, M.A. Ricci, F. Bruni and N.T. Skipper, J. Phys. Chem. B Vol. 111 (2007), 5610

[9] E. Charnaya, C. Tien, W. Wang, M. Lee, D. Miche, D. Yaskov, S. Sun and Y. Kumzerov, Phys. Rev. B Vol. 72 (2005), 035406

[10] H.K. Christenson, J. Phys.: Condens. Matt. 13 (2001), R95-R133

[11] W. Frank, C. Elsasser and M. Fähnle, Phys. Rev. Lett. 74 (1995), 1791-1794

[12] D.L. Price, K.S. Singwi and M.P. Tosi, Phys. Rev. B Vol. 2 (1970), 2983

[13] V.G. Vaks, M.I. Katsnelson, V.G. Koreshkov, A.I. Likhtenstein, O.E. Parfenov, V.F. Skok, V.A. Sukhoparov, A.V. Trefilov and A.A. Chernyshov, J. Phys.: Condens. Matt. Vol. 1 (1989), 5319

DOI: 10.1088/0953-8984/1/32/001

[14] R.O. Jones, A.I. Lichtenstein and J. Hutter, J. Chem. Phys. Vol. 106 (1997), 4566

[15] P.B. Balbuena and J.M. Seminario, Nanomaterials: Design and simulation, (Elsevier B.V., 2007)

[16] S. Lowell, J.E. Shields, M.A. Thomas and M. Thommes, Characterization of porous solids and powders: surface area, pore size and density-4th Ed. (Kluwer Academic Publishers, 2004)

DOI: 10.1007/978-1-4020-2303-3

[17] P. Huber, S. Grüner, C. Schäfer, K. Knorr and A.V. Kityk, Europ. Phys. J. Special Topics Vol. 141 (2007), 101

[18] H. Abe, K.I. Ohshima and T. Suzuki, J. Appl. Crystall. Vol. 27 (1994), 1040

[19] W.F. Brace and J.B. Walsh, American Mineralogist Vol. 47 (1962), 1111.