Thermoelectric properties of two stacking sequences of crystalline GST-225

Pseudobinary GeTe-Sb2Te3 compounds are widely used as phase-change
optical materials for DVD-RAM.[3] Ge2Sb2Te5 (GST-225) is used for
this propose but the stacking sequence of the stable crystal structure
is motive of debate. Pseudobinary compounds there are claimed to be
good thermoelectric materials due the large number of intrinsic structural
vacancies.[4] Thermoelectric properties for two proposed stacking sequences of GST-225 are computed using DFT[5, 6] and Boltzmann transport equation in the constant relaxation time approximation. After phonon calculations, no dynamic instabilities were found in the Irreducible Brillouin Zone for either of the proposed stacking sequences. One of the stacking sequences shows semiconductor-like density of states (DOS) with a computed gap of 190 meV unlike the other stacking sequence which has a metallic-like DOS. Thermoelectric properties calculation
reveals that semiconductor-like structure has the highest value of Seebeck coeffcient (SC).