Investigation of Structural Properties of n-Hexane and Decane Under Different Cooling Regimes by Raman Spectroscopy

Yurievich S.D. Beibitbekuly T.A. Sergeyevich K.Y. Dmitrievich F.V. Ualievich A.A.
November 2025 Multidisciplinary Digital Publishing Institute (MDPI)

Crystals
2025 #15 Issue 11

The glass-forming ability of short-chain alkanes remains a fundamental challenge in condensed matter physics. This study investigates the structural properties of n-hexane (C₆H₁₄) and decane (C₁₀H₂₂) under two distinct cooling regimes using Raman spectroscopy: fast cooling (~50–100 K/s via contact freezing on a copper substrate at 77 K) and conventional cooling (~1–5 K/s). Despite employing rapid cooling protocols, both alkanes underwent crystallization without forming amorphous phases. n-Hexane formed a defective crystalline structure characterized by broad spectral bands (FWHM ~40–45 cm⁻¹) and diffuse phase transitions in the 180–200 K range, while decane exhibited highly ordered crystalline structures with sharp spectral features (FWHM ~15–20 cm⁻¹) and abrupt transitions at 220–240 K. Quantitative analysis of characteristic Raman bands (skeletal deformations, C-C stretching, and C-H stretching vibrations) revealed fundamental differences in crystallization mechanisms related to molecular chain length. The study demonstrates that contact freezing methods are fundamentally incapable of achieving the extreme cooling rates (>10⁴ K/s) and ultra-thin film conditions (<1 μm) necessary for alkane vitrification. These findings establish spectroscopic diagnostic criteria for distinguishing between defective and well-ordered crystalline structures and define the limitations of conventional cryogenic techniques for glass formation in alkanes.

alkanes , cooling rate , crystallization , decane , glass transition , n-hexane , phase transitions , Raman spectroscopy

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Department of Thermal Physics and Technical Physics, Al-Farabi Kazakh National University, Al-Farabi Av. 71, Almaty, 050040, Kazakhstan
Department of Machines and Devices of Manufacturing Processes, Almaty Technological University, Tole Bi Av. 100, Almaty, 050012, Kazakhstan

Department of Thermal Physics and Technical Physics
Department of Machines and Devices of Manufacturing Processes

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