* Corresponding author. E-mail address: cesar.talon@uam.es (Ce H sar Talo H n) Physica B 284}288 (2000) 1155}1156 Low-temperature speci"c heat of molecular glasses and crystals Ce H sar Talo H n*, Miguel A. Ramos, Sebastia H n Vieira Laboratorio de Bajas Temperaturas, Departamento de Fn & sica de la Materia Condensada, C-III, Instituto Nicola & s Cabrera, Universidad Auto & noma de Madrid, Cantoblanco E-28049, Madrid, Spain Abstract We have measured the low-temperature speci"c heat C  of several glass-forming alcohols. Special attention has been paid to ethanol, either hydrogenated or deuterated, in its di!erent solid phases (fully ordered crystal, disordered crystal or orientational glass, and true structural glass). New measurements have been carried out on 1- and 2-propanol (for crystal and glass states) and on the glass phase of glycerol. The comparison of the isotopic e!ects in ethanol, as well as that with two isomers of propanol, provide a unique benchmark to study the relative importance of di!erent kinds of disorder. In this work, the whole set of maxima in C  /¹ is discussed in the framework of the scaling procedure of Liu and Lo K hneysen [Europhys. Lett. 33 (1996) 617].  2000 Elsevier Science B.V. All rights reserved. PACS: 63.50.#x; 64.70.Pf; 65.40.#g Keywords: Disordered solids; Molecular glasses; Speci"c heat 1. Introduction Since the pioneering work of Zeller and Pohl [1], it has been well known that the low-temperature properties of glasses present clear di!erences compared to crystalline materials. The investigation of such anomalies has led several authors to look for correlations which could feature that universal behaviour found in glasses. We have carried out low-temperature speci"c heat measurements of hydrogen-bonded molecular materials, that are liquid at room temperature, in crystalline and glassy states. In particular, we have studied both normal hydrogenated and fully deuterated ethanol, which ex- hibits a rich polymorphism, presenting fully ordered crystal, orientational glass, and structural glass phases [2,3]. We have also investigated the behaviour of two di!erent isomers of the same substance, 1- and 2-pro- panol both for crystalline and glassy states [4], as well as the glass phase of glycerol. In the present work, we will compile and discuss all these experimental data following the scaling proposed by Liu and Lo K hneysen [5]. 2. Experimental results and discussion Low-temperature speci"c heat measurements of di!er- ent alcohol samples were performed using a copper calorimetric cell [3]. In Fig. 1, we show the measured speci"c heat of all the above-mentioned molecular glass- es and crystals, plotted as C  /¹ versus temperature ¹ in a semilogarithmic scale. It has been argued that the origin of the observed `humpa in C  /¹ is somewhat di!erent for crystalline than for glassy states in ethanol [2], a subject which is still a general matter of discussion. In the case of propanol, it is remarkable that, while keeping the same molecular weight, the broad C  /¹ maxima vary appreciably. On the contrary, the isotopic e!ect in ethanol is correlated with the change in its molecular weight [3]. Liu and Lo K hneysen [5] have suggested a general cor- relation between the mechanisms leading to the C  /¹ maximum at intermediate temperatures in crystalline and amorphous solids. They plotted the height P  of the maximum of C  /¹ versus its position ¹  for a wide set of materials, mainly amorphous polymers and metals, as well as typical network glasses and their corresponding crystalline solids (see Fig. 2), "nding an approximate general correlation P  J¹  . In order to further inves- tigate this universal scaling, we have also depicted in 0921-4526/00/$ - see front matter  2000 Elsevier Science B.V. All rights reserved. PII: S 0 9 2 1 - 4 5 2 6 ( 9 9 ) 0 2 5 6 8 - 5