Ab initiocalculations of thermomechanical properties and electronic structure of vitreloyZr41.2Ti13.8C

Abstract

The thermo-mechanical properties and electronic structure of vitreloy (Zr 41.2 Ti 13.8 Cu 12.5 Ni 10 Be 22.5) are investigated using accurate ab initio molecular dynamic (AIMD) simulations and ab initio calculations. The structure of the model with 512 atoms is validated by comparison to the experimental data with calculated thermo mechanical properties in good agreement with the exisitng measurements. Detailed calculation of the electronic structure and bonding at the density functional level is obtained for the first time. It is revealed that the traditional definition of bond length in metallic glasses has a limited interpretation, and any theory based on geometrical consideration of the their values for discussion on the structural units in metallic glasses has similarly limited applications. On the other hand, we advocate the use of quantum mechanical based metric, the total bond order desity (TBOD) and their partial compoents or PBOD as valauble parameters to characterise the interatomic bonding in multi-component glasses such as vitrloy.

Review on Quantum Mechanically Guided Design of Ultra-Strong Metallic Glasses

“…To evaluate the relevance of the ab initio structures, the topology of the simulated samples is compared to the topology of the experimental samples. If the overall topologies are consistent, the structural analysis of the prediction often yields more detail than experimental studies (Qin et al, 2007;Ganesh and Widom, 2008;Hui et al, 2008b;Fang et al, 2009;Fujita et al, 2009;Hui et al, 2009;Hirata et al, 2011;Tian et al, 2011;Durandurdu, 2012;Wu et al, 2012;Zhang et al, 2015;Huang et al, 2016;Hunca et al, 2016;Yu et al, 2016). However, the electronic structure of metallic glasses is analyzed in only few studies (Hostert et al, 2011;Hunca et al, 2016;Schnabel et al, 2016aSchnabel et al, , 2017.…”

“…As the selection of reliable interatomic potentials for classical, semi-empirical potential molecular dynamics (MD) is challenging due to the anharmonicity in metallic glasses (Lambson et al, 1986;Crespo et al, 2016;Aitken et al, 2018), density functional theorybased ab initio MD has been used to calculate the properties of a vast number of materials as it does not require the input of interatomic potentials while being able to cover many-body interactions. By ab initio modeling, an in-depth analysis of the structure-property relationship of metallic glasses is possible that is otherwise challenging to probe only by experimental means, including parameters such as the partial pair correlations (Qin et al, 2007;Ganesh and Widom, 2008;Hui et al, 2008bHui et al, , 2009Fang et al, 2009;Tian et al, 2011;Zhang et al, 2015;Hunca et al, 2016;Yu et al, 2016), coordination polyhedra (Ganesh and Widom, 2008;Fang et al, 2009;Fujita et al, 2009;Hui et al, 2009;Hirata et al, 2011;Tian et al, 2011;Durandurdu, 2012;Wu et al, 2012;Zhang et al, 2015;Huang et al, 2016;Yu et al, 2016) and bonding Hunca et al, 2016). However, modeling the dynamics involved in relaxation and rejuvenation phenomena is out of reach for ab initio molecular dynamics due to the limitations of time steps and cell size as discussed below.…”

“…Alternative approaches to obtain an amorphous configuration include: stepwise cooling to simulate a cooling rate (Hui et al, 2008b;Fang et al, 2009;Fujita et al, 2009;Hirata et al, 2011;Tian et al, 2011;Durandurdu, 2012;Wu et al, 2012;Hunca et al, 2016;Yu et al, 2016); cooling a supercell from melt, equilibration below the melting point and subsequent cooling to room temperature with an imposed cooling rate (Qin et al, 2007;Jakse and Pasturel, 2008;Hui et al, 2009;Huang et al, 2016); or by conducting several tempering steps (Ganesh and Widom, 2008;Hui et al, 2008a). Thereby, structures consistent with physical samples can be achieved (Galván-Colín et al, 2015).…”

“…The coefficient of thermal expansion had been predicted by the volume change of an ab initio configuration as a function of the temperature (Hunca et al, 2016), which is rather expensive in terms of computational resources. Theoretically, the thermal expansion coefficient of metallic glasses can be predicted by the Debye-Grüneisen model.…”

First‐principles study in an inter‐granular glassy film model of silicon nitride

“…The OLCAO method uses atomic orbitals for the basis function expansion and is particularly effective for the electronic structure of large complex systems. The combination of VASP for structural optimization and OLCAO for properties evaluation has been successfully demonstrate in many crystalline and noncrystalline materials, and also in complex biomolecular systems . In the present calculation, the basis consists of 1s, 2s, 2p, 3p, and 3d orbitals for Si and 1s, 2s, 2p orbitals for N and O.…”