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Free Energy Simulation Of Grain Boundary Segregation And Thermodynamics In Ni3−Xal1+X, R. Najafabadi, H.Y. Wang, D. J. Srolovitz, Richard Alan Lesar
Free Energy Simulation Of Grain Boundary Segregation And Thermodynamics In Ni3−Xal1+X, R. Najafabadi, H.Y. Wang, D. J. Srolovitz, Richard Alan Lesar
Richard Alan Lesar
The free energy simulation method is employed to study segregation to Σ5 and Σ13 (001) twist grain boundaries and their free energies in ordered Ni3−xAl1+x. In the temperature range studied (300–900K), it is shown that there is almost no segregation, strong Al segregation, and weak Ni segregation to the grain boundary for the stoichiometric, Al-rich, and Ni-rich bulk compositions respectively. It is also shown that the segregation is limited to a few (002) planes around the grain boundary and its magnitude decreases with increasing temperature. For Al-rich bulk composition, it is demonstrated that segregation at low temperature substantially lowers the …
Finite Temperature Structure And Thermodynamics Of The Au Σ5 (001) Twist Boundary, R. Najafabadi, D. J. Srolovitz, Richard Alan Lesar
Finite Temperature Structure And Thermodynamics Of The Au Σ5 (001) Twist Boundary, R. Najafabadi, D. J. Srolovitz, Richard Alan Lesar
Richard Alan Lesar
The structure and thermodynamic properties of a Σ5 (001) twist boundary in gold are studied as a function of temperature. This study was performed within the framework of the Local Harmonic (LH) model and employed an Embedded Atom Method (EAM) potential for gold. We find that for the Σ5 (001) twist boundary in gold, a distorted CSL structure is stable at low temperatures, but undergoes a phase transformation to a DSC related structure near room temperature. This transformation is shown to be first order. The temperature dependences of the excess grain boundary free energy, enthalpy, entropy, specific heat, and excess …
Calculated Thermodynamic Properties And Phase Transitions Of Solid N2 At Temperatures 0≤T≤300 K And Pressures 0≤P≤100 Gpa, J. Belak, Richard Alan Lesar, R. D. Etters
Calculated Thermodynamic Properties And Phase Transitions Of Solid N2 At Temperatures 0≤T≤300 K And Pressures 0≤P≤100 Gpa, J. Belak, Richard Alan Lesar, R. D. Etters
Richard Alan Lesar
Thermodynamic properties of solid nitrogen are calculated over a variety of isotherms and isobars using a constant pressure Monte Carlo method with deformable, periodic boundary conditions. Vibron frequencies are calculated using a simple perturbation theory. In addition, pressure–volume relations, thermal expansion coefficients, structures, and phase transition pressures and temperatures are determined. In particular, the nature of the orientational disorder in the plastic crystal phases is examined by calculating a variety of orientational order parameters.
Location Of Melting Point At 300 K Of Nitrogen By Monte Carlo Simulation, Evert Jan Meijer, Daan Frenkel, Richard Alan Lesar, Anthony J.C. Ladd
Location Of Melting Point At 300 K Of Nitrogen By Monte Carlo Simulation, Evert Jan Meijer, Daan Frenkel, Richard Alan Lesar, Anthony J.C. Ladd
Richard Alan Lesar
We present an accurate new method to compute absolute free energies of molecular solids by computer simulations. As a first application, we computed the thermodynamicphase transition between the fluid phase and the orientational disordered solid β phase of nitrogen at 300 K, using a well tested pair potential. The computed coexistence pressure and the volume change coincides within the error margins with the experimental values. The coexistence volume differed by 2% from the experimental value. To our knowledge these results constitutes the first numerical calculation of the thermodynamic stability for a model of a realistic molecular solid.