ترغب بنشر مسار تعليمي؟ اضغط هنا

First principles investigation on anomalous lattice shrinkage of W alloyed rock salt GeTe

127   0   0.0 ( 0 )
 نشر من قبل Guanjie Wang
 تاريخ النشر 2020
  مجال البحث فيزياء
والبحث باللغة English




اسأل ChatGPT حول البحث

According to Vegards law, larger radius atoms substitute for smaller atoms in a solid solution would enlarge the lattice parameters. However, by first-principles calculations, we have observed unusual lattice shrinkage when W replaces Ge in rock salt GeTe. We attribute this anomalous contract to the larger electronegativity difference between W and Te than between Ge and Te, which results in shorter W-Te bonds and pronounced local distortion around W dopants. The present work would provide new insight into the lattice parameter determination and a deeper understanding of the structural properties of ternary solid solutions.

قيم البحث

اقرأ أيضاً

We combine ab initio simulations and Raman scattering measurements to demonstrate explicit anharmonic effects in the temperature dependent dielectric response of a NaCl single crystal. We measure the temperature evolution of its Raman spectrum and co mpare it to both a quasi-harmonic and anharmonic model. Results demonstrate the necessity of including anharmonic lattice dynamics to explain the dielectric response of NaCl, as it is manifested in Raman scattering. Our model fully captures the linear dielectric response of a crystal at finite temperatures and may therefore be used to calculate the temperature dependence of other material properties governed by it.
203 - Yue Chen , Xinyuan Ai , 2013
Here we introduce a new approach to compute the finite temperature lattice dynamics from first-principles via the newly developed slave mode expansion. We study PbTe where inelastic neutron scattering (INS) reveals strong signatures of nonlinearity a s evidenced by anomalous features which emerge in the phonon spectra at finite temperature. Using our slave mode expansion in the classical limit, we compute the vibrational spectra and show remarkable agreement with temperature dependent INS measurements. Furthermore, we resolve experimental controversy by showing that there are no appreciable local nor global spontaneously broken symmetries at finite temperature and that the anomalous spectral features simply arise from two anharmonic interactions. Our approach should be broadly applicable across the periodic table.
Different stoichiometric configurations of graphane and graphene fluoride are investigated within density functional theory. Their structural and electronic properties are compared, and we indicate the similarities and differences among the various c onfigurations. Large differences between graphane and graphene fluoride are found that are caused by the presence of charges on the fluorine atoms. A new configuration that is more stable than the boat configuration is predicted for graphene fluoride. We also perform GW calculations for the electronic band gap of both graphene derivatives. These band gaps and also the calculated Youngs moduli are at variance with available experimental data. This might indicate that the experimental samples contain a large number of defects or are only partially covered with H or F.
109 - Yini Lv , Kaige Hu , Shulong Wen 2019
Alloying elements play an important role in the design of plasma facing materials with good comprehensive properties. Based on first-principles calculations, the stability of alloying element W and its interaction with vacancy defects in Ta-W alloys are studied. The results show that W tends to distribute dispersedly in Ta lattice, and is not likely to form precipitation even with the coexistence of vacancy. The aggregation behaviors of W and vacancy can be affected by their concentration competition. The increase of W atoms has a negative effect on the vacancy clustering, as well as delays the vacancy nucleation process, which is favorable to the recovery of point defects. Our results are in consistent with the defect evolution observed in irradiation experiments in Ta-W alloys. Our calculations suggest that Ta is a potential repairing element that can be doped into Ta-based materials to improve their radiation resistance.
Ferroelectric domain walls are boundaries between regions with different polarization orientations in a ferroelectric material. Using first principles calculations, we characterize all different types of domain walls forming on ($11bar{1}$), ($111$) and ($1bar{1}0$) crystallographic planes in thermoelectric GeTe. We find large structural distortions in the vicinity of most of these domain walls, which are driven by polarization variations. We show that such strong strain-order parameter coupling will considerably reduce the lattice thermal conductivity of GeTe samples containing domain walls with respect to single crystal. Our results thus suggest that domain engineering is a promising path for enhancing the thermoelectric figure of merit of GeTe.
التعليقات
جاري جلب التعليقات جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
mircosoft-partner

هل ترغب بارسال اشعارات عن اخر التحديثات في شمرا-اكاديميا