High pressure structural phase transition and electronic properties have been investigated using the linear combination of atomic orbitals (LCAO) method with two exchangecorrelation approximations, the generalized gradient approximation (GGA) and local density approximation (LDA). The present study shows phase transitions from B1 to B27 and B27 to B2 at 6.24 GPa and 16.39 GPa, respectively. Lattice constant, bulk modulus, and energy gap of pressureinduced PbSe are found to be in good agreement with previous theoretical and experimental results. Variation of electronic band structure with pressure shows direct band gap along
Systematic studies of IV–VI semiconductor compounds on theoretical as well as experimental background have given overwhelming properties which not only are important for the scientific inquest but have wide scale technological applications [
Such fascinating properties of the IV–VI semiconductor compounds become a subject of extensive research on the lead chalcogenides PbX (X = S, Se, Te). On account of narrow forbidden gap of PbSe ~0.26 eV (300 K), anomalous order of band gap, and low thermal conductivity, it appeared to be a potential candidate for the technological applications in the field of thermoelectric devices [
Excellent properties of this material were aggravated to investigate pressureinduced structural and electronic properties. In the last few decades, a number of investigations on its pressureinduced phase transition and structural properties have been reported; see, for example, [
Quantum mechanical periodic LCAO calculations for the ground state total crystal energy are performed using the computer code CRYSTAL06 [
The cohesive energy [
The structural parameters were theoretically evaluated first by calculating the total lattice energies over a set of different volumes around the equilibrium values and then were fitted to the third order BirchMurnaghan equation of state (EOS) using the following relations:
Calculated equilibrium lattice parameter (
Parameters  Present calculations  Experimental results  Other calculations  

GGA  LDA  
NaCltype, B1 phase  

6.08  6.17  6.117 [ 
6.211 [ 

66.96  64.72  28.8 [ 
48.27 [ 

4  3.7  4.1 [ 
4.35 [ 

6.95  —  —  7.39 [ 


Orthorhombic Pnma phase (B27, FeB type)  
















68.94  65.5  —  — 

4.9  4.9  —  — 


CsCltype, B2 phase  

3.709  3.74  3.379 [ 
— 

70  64.72  —  62.0 [ 

3.9  3.7  —  2.40 [ 
Figures
The calculated energy versus volume for B1, B27, and B2 phases of PbSe: using the PBE (a) and VBH (b) correlation functional. The scattered points show calculated energies and the solid lines show the fitted
In order to investigate the phase transition pressure (
Enthalpy versus pressure calculated from firstprinciples total energy for the B1, B27, and B2 structures of PbSe using the PBE (a) and VBH (b) correlation functional.
These investigated transition pressures are reported in Table
Transition pressure (in GPa) for PbSe.
Transition  Present  Experimental  Other calculations  

GGA  LDA  
B1 → B27  6.24  7.97  4.5 [ 
7.45 [ 
B27 → B2  16.39  18.25  16.0 [ 
18.76 [ 
The pressure versus volume data for B1, B27, and B2 phases were computed, using the calculated values of
Variation of volume with increasing pressure for PbSe using GGA.
Knowledge of energy band gaps at different pressure is important to provide the information about their potential efficiency in fabricating various optoelectronic and thermoelectronic devices. In order to compute the energy band gap at different pressures, the equilibrium lattice constants are used and different symmetry points like
Band gap of PbSe in B1 phase at different pressures.
Pressure 
Present calculation  Other calculations 

−4  0.338  — 
−2  0.252  — 
0  0.185  0.21 [ 
2  0.118  — 
4  0.05  — 
As seen from Figure
Energy band structure of PbSe in B1 phase.
Since the band structures at all considered pressures are similar with only a small change around the Fermi level, it is desirable to present band structure of B1 phase only at zero pressure (Figure
Variation of the energy band gap of PbSe under pressure. The solid line shows the linear fit and the dots show the calculated values.
The pressureinduced phase transition and electronic properties of PbSe investigated using LCAO method were found to be in good agreement with previous theoretical and experimental results. The intermediate phase of PbSe between B1 and B2 phases is found to be B27 phase. The variation of energy band gap of PbSe under pressure is reported and it is found that, unlike II–VI and III–V compounds, PbSe shows direct band gap at
The authors declare that there is no conflict of interests regarding the publication of this paper.
This work is financially supported by the CSIR, New Delhi, through the major Research Project no. 03 (1205)/12EMRII, dated 12 April, 2012.