Out-of-Equilibrium Polymorph Selection in Nanoparticle Freezing

Abstract

The ability to design synthesis processes that are out of equilibrium has opened the possibility of creating nanomaterials with remarkable physicochemical properties, choosing from a much richer palette of possible atomic architectures compared to equilibrium processes in extended systems. In this work, we employ atomistic simulations to demonstrate how to control polymorph selection via the cooling rate during nanoparticle freezing in the case of Ni3Al, a material with a rich structural landscape. State-of-the-art free-energy calculations allow us to rationalize the complex nucleation process, discovering a switch between two kinetic pathways, yielding the equilibrium structure at room temperature and an alternative metastable one at higher temperature. Our findings address the key challenge in the synthesis of nanoalloys for technological applications, i.e., rationally exploiting the competition between kinetics and thermodynamics by designing a treatment history that forces the system into desirable metastable states.

Modeling the mechanical properties of nanoparticles: a review

“…Concerning alloys, a careful consideration was given to 〈100〉-oriented Ni 3 Al nanocubes for their role as strengthening main constituent of γ/γ superalloys [54,98,99]. Ni 3 Al exhibits the L1 2 crystal structure i.e., a binary FCC-like structure with Ni atoms at mid-surface positions [124]. As a consequence, Ni 3 Al plastic deformation relies on 〈110〉{111} superdislocation with a Burgers vector twice larger than in usual FCC metals [125,126].…”

Nonclassical Nucleation of Zinc Oxide from a Physically Motivated Machine-Learning Approach

“…A better understanding of crystallization would allow for rational control of material engineering and possibly for the development of novel functional materials and technological applications. From the fundamental point of view, numerous works have been dedicated to elucidating the emergence of the nucleation core − and its role in controlling the final crystal structure. − For instance, it is now possible to observe the crystal birth with electron microscopy, ,,− and colloidal science has also provided numerous experimental results on nucleation. − Yet, numerical simulations remain the principal instrument to investigate crystallization at the atomistic level . In this context, most of these works require large-scale simulations in order to observe phase transition and have therefore only focused on materials for which the interactions are very simple, including hard spheres, ,− Lennard-Jones, ,,,, water, ,− as well as metallic potentials, such as embedded-atom model. ,, …”

“…20 In this context, most of these works require large-scale simulations in order to observe phase transition and have therefore only focused on materials for which the interactions are very simple, including hard spheres, 3,21−25 Lennard-Jones, 1,5,9,11,26 water, 23,27−34 as well as metallic potentials, such as embedded-atom model. 8,10,35 Prompted by this large body of fundamental achievements, it becomes timely to reach the same level of understanding for crystallization in more complex materials in order to target more diverse technological applications. So far, the need for large-scale simulations has prevented using quantum-accurate modeling including density functional theory (DFT), and the research field dedicated to constructing novel interaction potentials to bridge this computational gap has been ever expanding.…”

Non-classical nucleation of zinc oxide from a physically-motivated machine-learning approach

“…Better understanding crystallization would allow for a rational control of material engineering and possibly the development of novel functional materials and technological applications. From the fundamental point of view, numerous works have been dedicated to elucidating the emergence of the nucleation core [1][2][3][4][5] and its role in controlling the final crystal structure [6][7][8][9][10][11][12]. For instance, it is now possible to observe the crystal birth with electron microscopy [6,7,[13][14][15], and colloidal science has also provided numerous experimental results on nucleation [16][17][18][19].…”

“…Yet, numerical simulations remain the principle instrument to investigate crystallization at the atomistic level [20]. In this context, most of these works require large scale simulations in order to observe the phase transition and have therefore only focused on materials for which the interactions are simple including hard-spheres [4,[21][22][23], Lennard-Jones [2,5,9,11], water [23][24][25][26][27][28][29][30][31], as well as metallic potentials like embeddedatom model (EAM) [8,10,32].…”