Sevenfold Coordinated MgSe: Experimental Internal Atom Position Determination to 146 GPa, Diffraction Studies to 202 GPa, and Theoretical Studies to 500 GPa

Abstract

MgSe has been studied using energy dispersive x-ray diffraction to 202 GPa and local density approximation and ultrasoft pseudopotentials to 500 GPa. MgSe undergoes a "continuous" phase transformation from the rocksalt to FeSi (B28) beginning at around 99 6 8 GPa and approaching sevenfold coordination at 202 GPa. Theoretical computation finds the B28 transition beginning at 58 GPa followed by a transition to an orthorhombic distortion of the B2 structure at 429 GPa.[S0031-9007(98)

Phase transition and thermodynamic properties of MgTe under high pressure

“…[18] microscopic point of view. The calculated equilibrium lattice constants a, elastic constants C ij , zero-pressure bulk modulus B 0 and its pressure derivation B 0 from the Birch-Murnaghan equation of state (EOS) [17] are listed in Table 1, together with other theoretical results [5][6][7][18][19][20][21][22][23][24][25][26][27]4] and the experimental data [28]. The agreements among them are good.…”

Phase transformation and elastic behavior of MgX (X=S, Se, Te) alkaline earth chalcogenides

“…Electronic band structure studies of these systems specifies that there are no d electrons available in the valence band and a energy gap of about 2.5-6 eV is documented. Under compression, a first-order phase transition from the sixfold-coordinated B1 structure to the eightfold-coordinated CsCl-type (B2) has been found in magnesium chalcogenides MgX (X ¼ S, Se, and Te) [5][6][7][8][9][10].…”

“…Ruoff et al [7] have studied MgSe using energy dispersive X-ray diffraction (EDXD) to 202 GPa and local density approximation and ultrasoft pseudopotential to 500 GPa. It is revealed that MgSe undergoes a continuous phase transformation from the rocksalt to FeSi (B28) beginning at around 9978 GPa and approaching sevenfold coordination at 202 GPa.…”

“…Motivated by the remarks on experimental and band structure studies [5][6][7][8][9][10][11][12][13] and the charge transfer effect approach [14] for the successful description of the phase transition and high pressure behavior of binary semiconductors, we thought it pertinent to employ the two-body interactions that includes vdW attraction, which is not explicitly accounted in band structure calculation in semiconducting compounds. We stress that the theoretical investigation on MgX compounds for the pressure dependent behavior of the second order elastic constants (SOEC) for B1 and B2 phase has not been carried out earlier due to lack of symmetry in structure.…”

Pressure‐induced structural phase transitions in materials and earth sciences

“…Recently, a theoretical prediction of the phase transition from the NiAs structure to the orthorhombic Pnma structure above 43 GPa has been published [101] despite no transition was found up to 60 GPa [100]. On the other hand, MgSe has been found to transit from the rocksalt to the FeSi structure around 100 GPa in relatively good agreement with calculations [102,103].…”