Use of massively parallel molecular dynamics simulations for radiation damage in pyrochlores

Todorov, Ilian T.; Allan, Neil L.; Purton, John A.; Dove, Martin T.; Smith, William R.

doi:10.1007/s10853-006-1323-x

Cited by 18 publications

(11 citation statements)

References 31 publications

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“…Examples are those of Chartier et al 18 , Devanathan 25 and pyrochlore studies by Purton and co-workers. 8,24,26 Very large (several-million-atom) damage cascade simulations have been performed by Trachenko and co-workers 27 These large cascade simulations push the boundaries of MD to the limit of current computational resources.…”

Section: Introductionmentioning

confidence: 99%

Order parameter and connectivity topology analysis of crystalline ceramics for nuclear waste immobilization

Archer¹,

Foxhall²,

Allan³

et al. 2014

J. Phys.: Condens. Matter

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We apply bond order and topological methods to the problem of analysing the results of radiation damage cascade simulations in ceramics. Both modified Steinhardt local order and connectivity topology analysis techniques provide results that are both translationally and rotationally invariant and which do not rely on a particular choice of a reference structure. We illustrate the methods with new analyses of molecular dynamics simulations of single cascades in the pyrochlores Gd2Ti2O7 and Gd2Zr2O7 similar to those reported previously (Todorov et al 2006 J. Phys Condes. Mat. 18 2217).Results from the Steinhardt and topology analyses are consistent, while often providing complementary information, since the Steinhardt parameters are sensitive to changes in angular arrangement even when the overall topological connectivity is fixed. During the highly non-equilibrium conditions at the start of the cascade, both techniques reveal significant localised transient structural changes and variation in the cationconnectivity. After a few picoseconds, the connectivity is largely fixed, while the order parameters continue to change. In the zirconate there is a shift to the anion disordered system while in the titanate there is substantial reversion and healing back to the parent pyrochlore structure.3

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Section: Introductionmentioning

confidence: 99%

Order parameter and connectivity topology analysis of crystalline ceramics for nuclear waste immobilization

Archer¹,

Foxhall²,

Allan³

et al. 2014

J. Phys.: Condens. Matter

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“…COMPASS (condensed-phase optimized molecular potentials for atomistic simulation studies) [10] is utilized for the simulation of organic and inorganic molecules and polymers. DL_POLY [11] is a general purpose MD software permitting user-defined potential functions. The DREIDING model [12] is useful for predicting structures and dynamics of organic, biological and main-group inorganic molecules.…”

Section: Molecular Dynamicsmentioning

confidence: 99%

Computational Methods for the Development of Polymeric Biomaterials

Costache¹,

Ghosh²,

Knight³

et al. 2010

Adv Eng Mater

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“…This calls into question the selection of SYNROC C related titanate phases, betafite (Ca,U)Ti2O7 8 and zirconolite CaZrTi2O7 9 as principal candidates for Pu-immobilization despite their apparent longevity in geological environments, where they are found as metamict phases. Gd2Ti2O7 is thus a useful model system because of the attention it has received both experimentally [10][11][12][13] and theoretically 6,[14][15][16][17][18][19][20][21][22] and its close similarity to the SYNROC C related titanate phases. The explanation for such different behaviour of two pyrochlores as closely related as Gd2Ti2O7 and Gd2Zr2O7 must ultimately lie at the atomic level and this remains the subject of much attention and conjecture 23 .…”

Section: Introductionmentioning

confidence: 99%

“…One powerful atomistic technique is molecular dynamics (MD) (e.g. Chartier et al, 29 Devanathan 20 , Trachenko et al 32 , Purton et al 6,16,22 , Foxhall et al 30 , Aidhy et al 33 ). Due to the large energy of the PKAs very large simulation cells are required, even reaching the order of several million atoms.…”

Section: Introductionmentioning

confidence: 99%

Multiple cascade radiation damage simulations of pyrochlore

Archer

Foxhall

Allan

et al. 2020

Molecular Simulation

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We report molecular dynamics simulations of multiple radiation damage cascades in the pyrochlores Gd2Ti2O7 and Gd2Zr2O7 and in the solid solution Gd2(ZrxTi1-x)2O7 (x = 0.25, 0.50, 0.75). Using a simulation cell of approximately 360,000 atoms, for each compound 2,200 decay events are simulated over a total time of 10 ns, with each recoiling uranium atom (primary knock on atom, PKA) being assigned an initial kinetic energy of 5 keV. The structures generated in the simulations are analysed using Steinhardt local order parameters. There is a large increase in volume for the Ti pyrochlore associated with a transition to an amorphous structure which resembles the melt while preserving the immediate local environment of the Ti. The calculated dose for amorphisation is approximately 20 eV atom -1 which compares well with experiment 1 . It appears to be the overlap of cascade and damage accumulation that drives the amorphisation and eventually suppresses the healing mechanisms. We have examined the variation in amorphous fraction with the number of decay events -an expression with two rather than one exponential terms reproduces the simulation data well. The behaviour of the zirconate is quite different -the substantial anion disorder produced by each recoil event is followed by healing between cascade events and reversion to the parent pyrochlore. In the solid solution the onset of amorphisation is delayed to successively later times on increasing the Zr concentration and the overall swelling reduced. Our simulations highlight the importance of ion mobility, associated with the weaker Zr-O bonds, in the healing process.

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Use of massively parallel molecular dynamics simulations for radiation damage in pyrochlores

Cited by 18 publications

References 31 publications

Order parameter and connectivity topology analysis of crystalline ceramics for nuclear waste immobilization

Order parameter and connectivity topology analysis of crystalline ceramics for nuclear waste immobilization

Computational Methods for the Development of Polymeric Biomaterials

Multiple cascade radiation damage simulations of pyrochlore

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