Thermal expansion coefficient of WRe alloys from first principles

Dengg, Thomas; Razumovskiy, Vsevolod I.; Romaner, Lorenz; Kresse, Georg; Puschnig, Peter; Spitaler, Jürgen

doi:10.1103/physrevb.96.035148

Cited by 19 publications

(5 citation statements)

References 41 publications

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“…The material parameters used in our calculations are summarized in Table 1; γ, v, n and ρ were obtained from ab-initio calculations, using ThermElpy [54] and Vienna Ab-initio Simulation Package (VASP) [55]. Here, γ is the high-temperature limit of the Grüneisen parameter, obtained by fitting Birch-Murnaghan equation of states and extracting the pressure derivative of the bulk modulus.…”

Section: Models For Phonon Scatteringmentioning

confidence: 99%

Thermal Characterization and Modelling of AlGaN-GaN Multilayer Structures for HEMT Applications

et al. 2020

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To optimize the thermal design of AlGaN-GaN high-electron-mobility transistors (HEMTs), which incorporate high power densities, an accurate prediction of the underlying thermal transport mechanisms is crucial. Here, a HEMT-structure (Al0.17Ga0.83N, GaN, Al0.32Ga0.68N and AlN on a Si substrate) was investigated using a time-domain thermoreflectance (TDTR) setup. The different scattering contributions were investigated in the framework of phonon transport models (Callaway, Holland and Born-von-Karman). The thermal conductivities of all layers were found to decrease with a temperature between 300 K and 773 K, due to Umklapp scattering. The measurement showed that the AlN and GaN thermal conductivities were a magnitude higher than the thermal conductivity of Al0.32Ga0.68N and Al0.17Ga0.83N due to defect scattering. The layer thicknesses of the HEMT structure are in the length scale of the phonon mean free path, causing a reduction of their intrinsic thermal conductivity. The size-effect of the cross-plane thermal conductivity was investigated, which showed that the phonon transport model is a critical factor. At 300 K, we obtained a thermal conductivity of (130 ± 38) Wm−1K−1 for the (167 ± 7) nm thick AlN, (220 ± 38) Wm−1K−1 for the (1065 ± 7) nm thick GaN, (11.2 ± 0.7) Wm−1K−1 for the (423 ± 5) nm thick Al0.32Ga0.68N, and (9.7 ± 0.6) Wm−1K−1 for the (65 ± 5) nm thick Al0.17Ga0.83N. Respectively, these conductivity values were found to be 24%, 90%, 28% and 16% of the bulk values, using the Born-von-Karman model together with the Hua–Minnich suppression function approach. The thermal interface conductance as extracted from the TDTR measurements was compared to results given by the diffuse mismatch model and the phonon radiation limit, suggesting contributions from inelastic phonon-scattering processes at the interface. The knowledge of the individual thermal transport mechanisms is essential for understanding the thermal characteristics of the HEMT, and it is useful for improving the thermal management of HEMTs and their reliability.

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Section: Models For Phonon Scatteringmentioning

confidence: 99%

Thermal Characterization and Modelling of AlGaN-GaN Multilayer Structures for HEMT Applications

et al. 2020

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“…Second, alloying elements are added to improve the materials properties. The effects of alloying may be unpredictable: Tungstenrhenium, e.g., shows an anomalous dependence of the thermal expansion on the Re content (Dengg et al, 2017) with a local minimum at around 12% Re. Third, crystallographic defects such as dislocations are introduced by mechanical treatment.…”

Section: Theory Of Defects In Metals and Metallic Compoundsmentioning

confidence: 99%

Perspectives on the Theory of Defects

Spitaler

Estreicher

2018

Front. Mater.

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Our understanding of defects in materials science has changed tremendously over the last century. While 100 years ago they were often ignored by scientists, nowadays they are in the spotlight of scientific interest and whole branches of technology have emerged from their skillful handling. The first part of this article gives a historical overview and discusses why defects are so important for modern material science. In the second part, we review the treatment of defects in semiconductors. We start by explaining the assumptions and approximations involved in ab-initio calculations and then discuss the treatment of defects in semiconductors. In the third part, we focus on defects in metals. We discuss the theoretical treatment of vacancies starting from experimental findings. The impact of improved theoretical techniques on the predictive power is discussed. This is illustrated with the role of vacancies in intermetallic compounds and random alloys. The last section deals with dislocations.

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“…Accurate information on the TE coefficient in the temperature dependence is required for the metallurgical industry as well as in engineering physics [3]. The TE coefficient is often used to determine the matching between different metal components in the alloy [4]. A large difference in the TE coefficients between the metal components can lead to adverse deformation in the alloy when the temperature changes [5].…”

Section: Introductionmentioning

confidence: 99%

“…In materials science, high precision measurements of lattice parameters using the X-ray method based on the development of the theory of the crystal structures have become increasingly important. Moreover, the accurate determination of lattice parameters enables one to investigate the TE coefficient of various crystalline substances, even if the weight of the substances available for measurement is only a few milligrams [2,4].…”

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Calculation of Temperature-Dependent Thermal Expansion Coefficient of Metal Crystals Based on Anharmonic Correlated Debye Model

Tien¹,

Thủy²,

Lien³

et al. 2023

Adv. technol. innov.

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This study aims to calculate the anharmonic thermal expansion (TE) coefficient of metal crystals in the temperature dependence. The calculation model is derived from the anharmonic correlated Debye (ACD) model that is developed using the many-body perturbation approach and correlated Debye model based on the anharmonic effective potential. This potential has taken into account the influence on the absorbing and backscattering atoms of all their nearest neighbors in the crystal lattice. The numerical results for the crystalline zinc (Zn) and crystalline copper (Cu) are in agreement with those obtained by the other theoretical model and experiments at several temperatures. The analytical results show that the ACD model is useful and efficient in analyzing the TE of coefficient of metal crystals.

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Thermal expansion coefficient of WRe alloys from first principles

Cited by 19 publications

References 41 publications

Thermal Characterization and Modelling of AlGaN-GaN Multilayer Structures for HEMT Applications

Thermal Characterization and Modelling of AlGaN-GaN Multilayer Structures for HEMT Applications

Perspectives on the Theory of Defects

Calculation of Temperature-Dependent Thermal Expansion Coefficient of Metal Crystals Based on Anharmonic Correlated Debye Model

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