Pressure Dependence of the Electronic Structure

The f band starts to overlap X3 at 6.04 A, the level X3 enters the f band at 6.0 A (onset of hybridization) and the X3 level appears below the f band at 5.86 A, i.e., the mixed valence state level is formed. The following energy parameters (ineV) are calculated as a function of the lattice constants a in A.  

The energy gap, Eg = Fis(f)-X3, varies with the lattice constant according to E = E°-3.9 (ao aj) with Eg = 0.60eV and ao = 6.20A. Literature data for the bulk modulus of K = 400 or 520 kbar yield dEg/dp = -20.2 and -15.5 meV/kbar, respectively, Farberovich [1]. The dependence on hydrostatic pressure dEg/dp= -11 meV/kbar is derived from optical absorption spectra by Kirk etal. [21], see also Jayaraman et al. [22,23,24]. The value -12meV/kbar is reported by Chatterjee et al. [25], and -14.8 meV/kbar by Bucher et al. [14] calculations with a model based on the compressibility curves of samarium and selenium ions give -7.7 meV/kbar, Narayan, Ramaseshan [16]. The deformation potential, 2 = (dEg/dp)Ko (with Ko=bulk modulus at room temperature), is -5.7 eV, Jayaraman etal. [22], also see [23, 24]. 

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