Ab-initio calculations for the structural properties of Zr-Nb alloys

Kharchenko, Vasyl O.; Kharchenko, Dmitrii O.

doi:10.5488/cmp.16.13801

Cited by 30 publications

(11 citation statements)

References 22 publications

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“…Zr and its alloys are indeed widely used as cladding materials in nuclear reactors. 25 At room temperature, Zr takes the hexagonal closed packed (HCP) phase and transitions into a body centered cubic (BCC) phase at higher temperature, which is dynamically unstable at 0 K. 6 Since phase stability is usually required to prevent structural failures in nuclear applications, understanding the temperature dependent vibrational dynamics of elemental Zr is critical. Recently, Zong et al successfully reproduced the phase diagram of Zr using a potential developed by kernel ridge regression algorithm, 26 indicating that ML could be a promising tool to model lattice dynamics of dynamically unstable crystals.…”

Section: Introductionmentioning

confidence: 99%

Temperature effect on the phonon dispersion stability of zirconium by machine learning driven atomistic simulations

Qian

Yang

2018

Phys. Rev. B

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It is well known that conventional harmonic lattice dynamics cannot be applied to dynamically unstable crystals at 0 K, such as high temperature body centered cubic (BCC) phase of crystalline Zr. Predicting phonon spectra at finite temperature requires the calculation of force constants to the third, fourth and even higher orders, however, it remains challenging to determine to which order the Taylor expansion of the potential energy surface for different materials should be cut off.Molecular dynamics, on the other hand, intrinsically includes arbitrary orders of phonon anharmonicity, however, its accuracy is severely limited by the empirical potential field used.Recently, machine learning algorithms emerge as a promising tool to build accurate potentials for molecular dynamics simulation. In this work, we approach the problem of predicting phonon dispersion at finite temperature by performing molecular dynamics simulations with machine learning-driven potential fields. We developed Gaussian approximation potential models for both the hexagonal closed-packed (HCP) phase and the body centered cubic (BCC) phase of Zirconium crystals. The developed potential field is first validated with static properties including energyvolume relationship, elastic constants and phonon dispersions at 0 K. Molecular dynamics

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Section: Introductionmentioning

confidence: 99%

Temperature effect on the phonon dispersion stability of zirconium by machine learning driven atomistic simulations

Qian

Yang

2018

Phys. Rev. B

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“…The dependence of the lattice parameter, a Zr , for β Zr-Nb alloys versus niobium concentration was previously evaluated in Ref. [25]. The authors have shown that with an increase in the niobium concentration the lattice constant decreases according to the linear law.…”

Section: Structure Optimizationmentioning

confidence: 99%

HYDROGEN DIFFUSION IN HCP Zr

García¹,

Ramunni²

2022

AnAFA

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We study the behavior of hydrogen (H) in theαandβphases of Zr and in theβphase of Nb, using the Siesta andVasp first principles codes based on the density functional theory (DFT). We calculate the hydrogen solution energy, the binding energy of the H-H and H-Nb complexes, as well as, the mixing energy of the Zr-Nb system. Furthermore, we have proposed a simple model for the study of the hydrogen diffusion (DH) mediated by interstitial mechanism in hcp Zr. We find that interstitial hydrogen diffuses isotropically according to DH=1.1×10−7exp(−42 KJ.mol−1/RT)(m2/s). Our results are in good agreement with experimental data and other Kinetic Monte Carlo (KMC) calculations. Finally, the formation energies of the three most stable hydrides in the hcp Zr phase were also calculated.

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“…For example: the elastic moduli of Zr single crystal and their temperature dependence were experimentally studied early in 1964 by Fisher and coworker [10]; the elastic constants of Nb single crystal were experimentally studied at 27 • C by Bolef [11]; the elastic constants of Nb-rich alloys Nb-xZr with bcc structure from 4.2 • K up to room temperature were experimentally determined by Hayes and coworker [12] in 1973; and also from zero temperature to the melting point were studied both experimentally and theoretically by Ashkenazi and coworkers [13] in 1978. Varshni [14]; Fast, et al [15]; and Olsson [16] have investigated the temperature dependence of elastic constants of zirconium; Peng, et al have studied the pressure effect on stabilities of self-interstitials in hcp-zirconium using first-principles method [17]; Liu, et al [18]; Wang, et al [19]; have calculated the elastic constants of niobium at normal pressure and high pressures, respectively; Kharchenko, et al have investigated [20] the effect of Nb concentration on the lattice constants of Zr-xNb; Wang, et al [21]; Weck, et al [22]; Al-Zoubi, et al [23]; have investigated the elastic constants for Zr-Nb alloys; Xin, et al have studied the point defect properties (such as formation energies) in hcp and bcc Zr with trace solute Nb by ab initio calculations [24]. However, to our knowledge, the mechanical properties of Zr-xNb alloys in presence of defects have not been thoroughly investigated, which will be studied in the present work.…”

Section: Introductionmentioning

confidence: 99%

Elastic stiffness tensors of Zr–xNb alloy in the presence of defects: A molecular dynamics study

Basaadat

Payami

2019

Int. J. Mod. Phys. C

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In a nuclear reactor, the Zr-xNb alloy, which is used as a structural material in the core region, is irradiated by energetic particles that cause the atoms to be displaced from their lattice sites and giving rise to crystal defects. The local changes in the atomic arrangements lead to local deformations of the solid and thereby changes of its local mechanical properties. Understanding the mechanisms behind this evolution in the core region of a reactor, and its monitoring or controlling is a critical task in nuclear industry. In this work, using extensive molecular dynamics simulations, we have studied the effects of radiation damage on the local mechanical properties of Zr-xNb alloy. In the first step, the effect of Nb-concentration on the mechanical stability of homogeneous Zr-xNb alloy is investigated. In the second step, we have studied the local changes of the elastic constants due to local changes of the microstructure. These local changes include presence and accumulation of vacancies in the form of dislocation loops or voids, accumulation of Nb atoms in the form of clusters of different morphologies. This study covers both cases of T = 0 • K and finite temperatures up to T = 600 • K.

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Ab-initio calculations for the structural properties of Zr-Nb alloys

Cited by 30 publications

References 22 publications

Temperature effect on the phonon dispersion stability of zirconium by machine learning driven atomistic simulations

Temperature effect on the phonon dispersion stability of zirconium by machine learning driven atomistic simulations

HYDROGEN DIFFUSION IN HCP Zr

Elastic stiffness tensors of Zr–xNb alloy in the presence of defects: A molecular dynamics study

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