Physics Letters A 369 (2007) 222–225
Discontinuities in the speciﬁc heat of magnesium and associated latent heat
at pressure-induced structural phase transitions using a local ﬁrst principles
Gregorio Ruiz Chavarría
Insituto de Física, Universidad Nacional Autónoma de México, Apdo. Postal 20-364, C.P. 01000, México D.F., Mexico
Received 6 October 2006; received in revised form 15 February 2007; accepted 24 April 2007
Available online 29 April 2007
Communicated by J. Flouquet
After a successful application of a local ﬁrst principles pseudopotential to the study of the structural pressure-induced phase transition for
magnesium, I now use the same local ﬁrst principles type of pseudopotential, to study the speciﬁc heat as function of the pressure, at 300 K, in
the region around the predicted phase transitions. I found that the speciﬁc presents two discontinuities, one for each transition of phase. These
discontinuities are associated to the existence of latent heat at each transition, which has not been yet reported experimentally.
2007 Elsevier B.V. All rights reserved.
PACS : 61.50.Ks; 64.70.Kb; 65.40.-b
Keywords: Phase transition; Laten heat
The type of pseudopotential used in this study has been proved successfully in previous works for the prediction of interionic
potentials, phonons, the lattice speciﬁc heat, elastic constants, phonon limited resistivity, superconductivity, vacancy formation
energy, including the variation of all these properties with the pressure of several simple metals [1–10].
In previous work, I used this local ﬁrst principles pseudopotential to reproduce the reported hcp-bcc phase transition of mag-
nesium under high pressure . In the same work, a second phase transition, from bcc to fcc, is also predicted. However, the
predicted pressure value at which this transition occurs is not precise. Nevertheless, it is expected the second transition to exist .
In this work, I use again the same local ﬁrst principles pseudopotential and perform a study of the speciﬁc heat of magnesium at
constant volume as function of pressure, at 300 K.
We constructed the local ﬁrst principles pseudopotential using the unscreened pseudopotential form factor, V(q), which is given
by the expression
[1 − ε(q)]
where δn(q) is the Fourier transform of the δ(r), the electronic density of conduction, and ε(q) is the dielectric function .Using
this expression we constructed the interionic potential [12,13]
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