Shock-induced phase transformations in gallium single crystals by atomistic methods

Abstract

Utilizing a modified embedded atom method potential, we performed large-scale classical molecular dynamics simulations (with up to 50 million atoms) to investigate the response of Ga single crystals to shock compression along the three major orientations of the orthorhombic A11 ground state, i.e., [001], [010], and [100]. For weak shocks with particle velocity u p < 300 m/s, these defect-free single crystals respond elastically, but for stronger shocks, they undergo a structural phase transformation and then (for even stronger shocks) melt. For intermediate shock strengths (300 m/s < u p < 1.2 km/s) a split shock wave is formed, with an elastic precursor (uniaxial compression wave) leading the slower transformation wave. The transformed region consists of a mixed phase, with stripes of the product phase embedded into the uniaxially compressed parent phase, with the ratio of product to parent phase increasing with increasing shock strength, much like in martensitic phase transformations. Upon shock release from the free surface at the end of the sample, the transformation is reversed, leaving only some defects behind, which makes it difficult to experimentally investigate the structural transformation in shock-recovered samples. We investigated the structure produced by the shock and found it to be similar to the β phase of Ga which is obtained by supercooling from the liquid state. However, the product phase shows only half the period along [100] in the calculated diffraction pattern. Further investigation showed that this is due to a different stacking sequence in this direction, namely ABCD instead of AB for the β phase.

Dynamical and transport properties of liquid gallium at high pressures

“…The present study builds on this previous work by reporting simulations where both the convergence of supercell and k-point grid sizes were investigated, and by simulations performed along the principal Hugoniot up to a pressure of 150 GPa. We find that the calculated Hugoniot is in very good agreement with both the experimental data [11] and recent classical molecular dynamics calculations [18,19] performed using a Modified Embedded Atom Method (MEAM)…”

Anomalous properties and the liquid-liquid phase transition in gallium

“…[1][2][3][4][5][6][7][24][25][26] Elementary gallium is another interesting substance that shares some common features with water, e.g., having multisolid phases and negatively sloped melting line. [28][29][30][31][32][33][34] Tien et al 35 observed two separate peaks at 260 K and 220 K in the nuclear magnetic resonance (NMR) spectra of opal-confined gallium which is interpreted as the existence of two liquid gallium phases confined in opal. Using computer simulations, Jara et al 36 reported that gallium has two states of liquid, a) Author to whom correspondence should be addressed.…”

A molecular dynamics study of the role of grain size and orientation on compression of nanocrystalline Cu during shock

“…Over the last decade, MD simulations and experimental studies have been performed to explore solid-solid phase transformations in single crystals [21][22][23][24][25][26][27][28][29][30][31][32][33][34][35]. For example, Kadau et al [24] identified the role of shockwave strength on structural transformations in Ga single crystals. Cui et al [21] explored the role of nanovoid size on the BCC to HCP phase transformation in Fe during shock.…”