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Shear Modeling: Thermoelasticity at High Temperature and PRessure for Tantalum.

DE200515014351

Publication Date	2004
Personal Author	Orlikowski, D.; Soderlind, P.
Page Count	10
Abstract	For large-scale constitutive strength models the shear modulus is typically assumed to be linearly dependent on temperature. However, for materials compressed beyond the Hugoniot or in regimes where there is very little experimental data, accurate and validated models must be used. To this end, we present here a new methodology that fully accounts for electron- and ion-thermal contributions to the elastic moduli over broad ranges of temperature (<20,000 K) and pressure (<10 Mbar). In this approach, the full potential linear muffin-tin orbital (FP-LMTO) method for the cold and electron-thermal contributions is closely coupled with ion-thermal contributions. For the latter two separate approaches are used. In one approach, the quasi-harmonic, ion-thermal contribution is obtained through a Brillouin zone sum of strain derivatives of the phonons, and in the other a full anharmonic ion-thermal contribution is obtained directly through Monte Carlo (MC) canonical distribution averages of strain derivatives on the multi-ion potential itself. Both approaches use quantum-based interatomic potentials derived from model generalized pseudopotential theory (MGPT). For tantalum, the resulting elastic moduli are compared to available ultrasonic measurements and diamondanvil- cell compression experiments. Over the range of temperature and pressure considered, the results are then used in a polycrystalline averaging for the shear modulus to assess the linear temperature dependence for Ta.
Keywords	Thermoelasticity Tantalum High temperatures Elastic moduli Thermal explansion Temperature dependence Electrons High pressures Strain hardening Refractory metals Shear modeling
Source Agency	Technical Information Center Oak Ridge Tennessee
Corporate Authors	Lawrence Livermore National Lab., CA.; Department of Energy, Washington, DC.
Supplemental Notes	Sponsored by Department of Energy, Washington, DC.
Document Type	Technical Report
NTIS Issue Number	200521

Shear Modeling: Thermoelasticity at High Temperature and PRessure for Tantalum.

Shear Modeling: Thermoelasticity at High Temperature and PRessure for Tantalum.
DE200515014351

Publication Date	2004
Personal Author	Orlikowski, D.; Soderlind, P.
Page Count	10
Abstract	For large-scale constitutive strength models the shear modulus is typically assumed to be linearly dependent on temperature. However, for materials compressed beyond the Hugoniot or in regimes where there is very little experimental data, accurate and validated models must be used. To this end, we present here a new methodology that fully accounts for electron- and ion-thermal contributions to the elastic moduli over broad ranges of temperature (<20,000 K) and pressure (<10 Mbar). In this approach, the full potential linear muffin-tin orbital (FP-LMTO) method for the cold and electron-thermal contributions is closely coupled with ion-thermal contributions. For the latter two separate approaches are used. In one approach, the quasi-harmonic, ion-thermal contribution is obtained through a Brillouin zone sum of strain derivatives of the phonons, and in the other a full anharmonic ion-thermal contribution is obtained directly through Monte Carlo (MC) canonical distribution averages of strain derivatives on the multi-ion potential itself. Both approaches use quantum-based interatomic potentials derived from model generalized pseudopotential theory (MGPT). For tantalum, the resulting elastic moduli are compared to available ultrasonic measurements and diamondanvil- cell compression experiments. Over the range of temperature and pressure considered, the results are then used in a polycrystalline averaging for the shear modulus to assess the linear temperature dependence for Ta.
Keywords	Thermoelasticity Tantalum High temperatures Elastic moduli Thermal explansion Temperature dependence Electrons High pressures Strain hardening Refractory metals Shear modeling
Source Agency	Technical Information Center Oak Ridge Tennessee
Corporate Authors	Lawrence Livermore National Lab., CA.; Department of Energy, Washington, DC.
Supplemental Notes	Sponsored by Department of Energy, Washington, DC.
Document Type	Technical Report
NTIS Issue Number	200521