Abstract
Calcium at megabar pressures undergoes numerous structural transitions and has a complex phase diagram. At the same time, according to the recent theoretical investigations, an anomalous behavior of many physical properties, including a transition to the state of a narrow-gap semiconductor, can be expected even in the region of stability of the normal-pressure phase of calcium with the fcc structure at moderate pressures P ∼ 5–15 GPa. Data on the thermopower of calcium in the pressure range up to 9 GPa have been reported. The thermopower in this pressure range is positive, has a smooth maximum at 5–6 GPa, and decreases quite rapidly at higher pressures. The absolute values of the thermopower (5–12 μV/K) indicate that calcium in this pressure range is a metal. The difference between the thermopowers in the direct and inverse passages in the range of 5–7.5 GPa is fairly noticeable (∼10%). The possible reasons for such an anomalous behavior, as well as new calculations of the band structure of calcium, have been discussed.
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Original Russian Text © V.V. Brazhkin, O.B. Tsiok, M.V. Magnitskaya, 2013, published in Pis’ma v Zhurnal Eksperimental’noi i Teoreticheskoi Fiziki, 2013, Vol. 97, No. 8, pp. 561–565.
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Brazhkin, V.V., Tsiok, O.B. & Magnitskaya, M.V. Thermopower of calcium at high pressures. Jetp Lett. 97, 490–494 (2013). https://doi.org/10.1134/S0021364013080067
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DOI: https://doi.org/10.1134/S0021364013080067