Specific heat measurements in pure and in (Cu, Mn, Fe, Ni)-doped single-crystals of l-arginine phosphate monohydrate
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2010
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The influence of highly diluted impurities (Cu, Mn, Fe, Ni) on the temperature (T) dependence of the specific heat (cp) of l-arginine phosphate monohydrate (LAP) was investigated in the temperature range 1.8–300 K. The doped samples yielded values for cp in excess to those obtained for a pure LAP sample. The melting temperatures (Tm≈420 K) obtained by differential scanning calorimetry for pure and doped LAP samples were found not to be significantly affected by the impurities. The T-dependence of cp was fully accounted for by taking into consideration the Debye contribution, an Einstein term and a contribution due to both Frenkel and Schottky defects. The model fit all cp versus T data using a single value for both the Debye (θD=160 K) and the Einstein (TE=376.8 K) temperatures, and for the energy (εd=157.9 meV) required to create the defects.
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A. Organic compounds, B. Chemical synthesis, C. Differential scanning calorimetry (DSC), D. Specific heat
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MACHADO, F. L. A.; SOUSA, L. L. L.; CUNHA, R. O.; CABRAL, F. A.O.; RODRIGUES, A. R.; CARVALHO, J. F.; SANTANA, R. C. Specific heat measurements in pure and in (Cu, Mn, Fe, Ni)-doped single-crystals of l-arginine phosphate monohydrate. Journal of Physics and Chemistry of Solids, Amsterdam, p. 862-866, 2010. DOI: 10.1016/j.jpcs.2010.03.034. Disponível em: https://www.sciencedirect.com/science/article/pii/S0022369710000806, Acesso em: 25 maio 2023.