ترغب بنشر مسار تعليمي؟ اضغط هنا

Calculation of nanowire thermal conductivity using complete phonon dispersion relations

125   0   0.0 ( 0 )
 نشر من قبل Natalio Mingo
 تاريخ النشر 2003
  مجال البحث فيزياء
والبحث باللغة English
 تأليف N. Mingo




اسأل ChatGPT حول البحث

The lattice thermal conductivity of crystalline Si nanowires is calculated. The calculation uses complete phonon dispersions, and does not require any externally imposed frequency cutoffs. No adjustment to nanowire thermal conductivity measurements is required. Good agreement with experimental results for nanowires wider than 35 nm is obtained. A formulation in terms of the transmission function is given. Also, the use of a simpler, nondispersive Callaway formula, is discussed from the complete dispersions perspective.



قيم البحث

اقرأ أيضاً

The lattice dynamics of AgPd, Ni55Pd45, Ni95Pt05, and Cu0.715Pd0.285 intermetallic have been investigated using the DFT calculation. The phonon dispersions and phonon densities of states along for two symmetry directions are calculated by Weighted Dy namical Matrix (WDM) and compared with virtual crystal approximation (VCA), supercell approach, and inelastic neutron scattering experimental results. The impact of mass, force-constant fluctuation, and Ag concentration on lattice dynamics of AgPd are discussed, and a comparison between WDM and Supercell approach is performed. The averaged first Nearest Neighbor (1NN) force constants between various pairs of atoms in these intermetallic are obtained from the WDM approach. Based on our results, the WDM approach agrees well with the supercell approach, and neutron scattering experimental data. VCA overestimates in some cases and underestimates, in other cases, the first-principles frequencies.
376 - Zhao Wang , N. Mingo 2011
We theoretically compute the thermal conductivity of SiGe alloy nanowires as a function of nanowire diameter, alloy concentration, and temperature, obtaining a satisfactory quantitative agreement with experimental results. Our results account for the weaker diameter dependence of the thermal conductivity recently observed in Si$_{1-x}$Ge$_x$ nanowires ($x<0.1$), as compared to pure Si nanowires. We also present calculations in the full range of alloy concentrations, $0 leq x leq 1$, which may serve as a basis for comparison with future experiments on high alloy concentration nanowires.
We present a scheme for the improved description of the long-range interatomic force constants in a more accurate way than the procedure which is commonly used within plane-wave based density-functional perturbation-theory calculations. Our scheme is based on the inclusion of a q point grid which is denser in a restricted area around the center of the Brillouin Zone than in the remaining parts, even though the method is not limited to an area around Gamma. We have tested the validity of our procedure in the case of high-pressure phases of bulk silicon considering the bct and sh structure.
In recent years, nanostructuring of dielectric and semiconducting crystals has enhanced controllability of their thermal conductivity. To carry out computational material search for nanostructured materials with desirable thermal conductivity, a key property is the thermal conductivity spectrum of the original single crystal, which determines the appropriate length scale of nanostructures and mutual adaptability of different kinds of nanostructures. Although the first-principles phonon transport calculations have become accessible, the anharmonic lattice dynamics calculations are still heavy to scan many materials. To this end, we have developed an empirical model that describes the thermal conductivity spectrum in terms only of harmonic phonon properties and bulk thermal conductivity. The model was tested for several crystals with different structures and thermal conductivities, and was confirmed to reproduce the overall profiles of thermal conductivity spectra and their anharmonic calculations.
The heat transfer properties of the organic molecular crystal ${alpha}$-RDX were studied using three phonon-based thermal conductivity models. It was found that the widely used Peierls-Boltzmann model for thermal transport in crystalline materials br eaks down for ${alpha}$-RDX. We show this breakdown is due to a large degree of anharmonicity that leads to a dominance of diffusive-like carriers. Despite being developed for disordered systems, the Allen-Feldman theory for thermal conductivity actually gives the best description of thermal transport. This is likely because diffusive carriers contribute to over 95% of the thermal conductivity in ${alpha}$-RDX. The dominance of diffusive carriers is larger than previously observed in other fully ordered crystalline systems. These results indicate than van-der Waals bonded organic crystalline solids conduct heat in a manner more akin to amorphous materials than simple atomic crystals.
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