Thermodynamic and structural properties of the two isomers of solid propanol C. Tal  on a , M.A. Ramos a, * , S. Vieira a , Ivan Shmyt'ko b , Natalia Afonikova b , A. Criado c , G. Madariaga d , F.J. Bermejo e a Laboratorio de Bajas Temperaturas, Depto. de F  õsica de la Materia Condensada, C-III Instituto `Nicol  as Cabrera', Universidad Aut onoma de Madrid, Cantoblanco, 28049 Madrid, Spain b Institute of Solid State Physics RAN, Chernogolovka, Moscow, Russia c Depto. de F  õsica de la Materia Condensada, Universid de Sevilla, 41080 Sevilla, Spain d Depto. de F  õsica de la Materia Condensada, Universidad del Pa  õs Vasco, Bilbao, Spain e Consejo Superior de Investigaciones Cient  õ®cas, Serrano 123, 28006 Madrid, Spain Abstract We have measured the speci®c heat, C p , of the two chemical isomers of propanol, both at low temperatures 1.5±30 K) and around the glass-transition region  100 K. Although the two substances present only the stereoisomeric dierence, their glass-transition temperatures dier T g ' 98 K for 1-propanol and T g ' 115 K for 2-propanol), though with comparable changes in speci®c heat. At temperatures below 10 K, both isomers in the glassy state have the typical maximum in C p =T 3 . Nevertheless, the magnitude of the low-temperature speci®c heat is much larger in 2-propanol than in 1-propanol, a dierence which is also found in the Debye contributions in the corresponding crystalline states. To investigate the structural dierences between the two isomers of propanol, and their possible in¯uence on the ther- modynamic properties, X-ray scattering experiments have been performed on samples of the glassy and crystalline states. In the glassy state, both isomers present the expected amorphous pattern, with characteristic distances of 0:40  0:06 and 0:42  0:07 nm for 1- and 2-propanol, respectively. Preliminary structural analysis of the crystalline states would assign a triclinic structure for 1-propanol and a monoclinic structure for 2-propanol. Ó 2001 Elsevier Science B.V. All rights reserved. PACS: 65.40.+g; 64.70.Pf.; 61.43.Fs; 61.10.)i 1. Introduction The search for a deeper understanding of the properties of glassy materials at low temperature continues as a matter of interest and debate for the scienti®c community [1]. It is now accepted that the work of Zeller and Pohl [2] was the ®rst to establish that the low-temperature thermal prop- erties of glasses are universal, and dier from the properties observed in crystals. In particular, the speci®c heat of glasses depends linearly on tem- perature at T < 1 K, which was ascribed to the existence of tunneling states [3±5], whereas at temperatures T > 1K C p still deviates from the Debye T 3 dependence observed in crystals due to lattice vibrations, having a maximum in a C p =T 3 vs T plot. Journal of Non-Crystalline Solids 287 2001) 226±230 www.elsevier.com/locate/jnoncrysol * Corresponding author. Tel.: +34-91 397 5551; fax: +34-91 397 3961. E-mail address: miguel.ramos@uam.es M.A. Ramos). 0022-3093/01/$ - see front matter Ó 2001 Elsevier Science B.V. All rights reserved. PII:S0022-309301)00565-8