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Structure, elastic moduli and thermodynamics of sodium and potassium at ultra-high pressures

M. I. Katsnelson·G. V. Sinko·N. A. Smirnov·A. V. Trefilov·K. Yu. Khromov
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Abstract

The equations of state at room temperature as well as the energies of crystal structures up to pressures exceeding 100 GPa are calculated for Na and K . It is shown that the allowance for generalized gradient corrections (GGA) in the density functional method provides a precision description of the equation of state for Na, which can be used for the calibration of pressure scale. It is established that the close-packed structures and BCC structure are not energetically advantageous at high enough compressions. Sharply non-monotonous pressure dependences of elastic moduli for Na and K are predicted and melting temperatures at high pressures are estimated from various melting criteria. The phase diagram of K is calculated and found to be in good agreement with experiment.

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M. I. Katsnelson, G. V. Sinko, N. A. Smirnov, A. V. Trefilov, K. Yu. Khromov. 2000-03-30. Structure, elastic moduli and thermodynamics of sodium and potassium at ultra-high pressures. https://doi.org/10.1103/physrevb.61.14420

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