Molecular dynamics investigation of the size effect upon the β → α transformation in Zr nanocrystals

Study of size effects in structural transformations of bcc Zr films by molecular-dynamics simulation

“…Note that if the crystallite is held at an intermediate temperature, say, at T = 1000K for 1000 ps (1 million steps), the transition is not completed and the film part transformed to the hcp phase continuously travels through the crystallite without growing in size. A similar effect, i.e., the existence in a wide temperature range of an intermediate configuration of the uncompleted phase transition, was observed in studying the influence of the size of free nanocrystals on the β → α transformation in zirconium [27]). As seen in Fig.4, with increasing film thickness the temperature interval between the transition onset and completion decreases .…”

“…The spectrum was calculated with a Fourier transform of the function of atomic displacement time evolution averaged over an interval of 40 ps. The polarization vectors e k with wave vector k were calculated in the harmonic approximation as the eigenvalues of dynamical matrix for a bcc lattice with previously determined parameters corresponding to specified temperatures [27]. A comparison with the experimental data [28] shows that the potential chosen allows one to reproduce the experimentally observed features of the Zr phonon spectrum and their variation with temperature, including the softening of the transverse N-phonon with decreasing temperature, and so it may be used in simulating the thermal stability of bcc zirconium films.…”

“…In all variants, the calculation started with the formation of a crystallite with perfect bcc structure and (001) crystallographic orientation. The lattice parameter was chosen equal to its value in bulk bcc zirconium at the corresponding temperature [27]. The state of the sys- tem was followed up using the atomic radial distribution function (ARDF), the variation of the total energy, and visualization of both the crystallite as a whole and any separate crystallite plane.…”

Molecular dynamics simulation of phase competition in terbium

“…First, we performed a simple simulation described in Ref. 41. A single bcc crystal sample in the form of a cube with free surfaces normal to the [100], [010], and [001] directions containing 27 648 atoms was heated from T = 300 K to 1600 K with the rate of 10 12 K/s.…”

Study of peculiarities of the thermal expansion of zirconium thin films by molecular-dynamics simulation

“…[12] it was shown that this potential allows one to obtain, to a high degree of accuracy, the bcc and hcp lattice parameters of zirconium, cohesive energy, elastic constants, melting temperature, and other physical characteristics. The bulk phonon dispersion curves calculated with this potential along the symmetrical directions of the Brillouin zone of bcc zirconium at different temperatures were obtained in our paper [14]. A comparison with the experimental data shows that the potential chosen allows one to reproduce the experimentally observed features of the Zr phonon spectrum including the softening of the transverse N-phonon with decreasing temperature, and so it may be successfully used in calculating vibrational and thermal characteristics of zirconium films.…”