List of Journal Publications
2019
3.
Srinivasan, P., Duff, A. I., Mellan, T. A., Sluiter, M. H. F., Nicola, L., Simone, A.
The effectiveness of reference-free modified embedded atom method potentials demonstrated for NiTi and NbMoTaW Journal Article
In: MODELLING AND SIMULATION IN MATERIALS SCIENCE AND ENGINEERING, vol. 27, no. 6, 2019.
Abstract | BibTeX | Tags: interatomic potential fitting, Molecular dynamics, multi-component alloy, nickel titanium, Phase transformation, reference-free MEAM | Links:
@article{Srinivasan2019,
title = {The effectiveness of reference-free modified embedded atom method potentials demonstrated for NiTi and NbMoTaW},
author = {P. Srinivasan and A. I. Duff and T. A. Mellan and M. H. F. Sluiter and L. Nicola and A. Simone},
doi = {10.1088/1361-651X/ab2604},
year = {2019},
date = {2019-01-01},
journal = {MODELLING AND SIMULATION IN MATERIALS SCIENCE AND ENGINEERING},
volume = {27},
number = {6},
publisher = {Institute of Physics Publishing},
abstract = {One of the effective potentials that has proven to be very versatile and useful for describing metals is the modified embedded atom method (MEAM) potential. The reference-free version of the MEAM (RF-MEAM) potential provides more flexibility for fitting than the 2NN-MEAM because it also describes the pair potential as an explicit function. In this work, we present a methodology to fit RF-MEAM potentials to DFT data. We then evaluate the performance of the fitted potential by comparing MD simulations with experimental and DFT data. As an example, the methodology is applied to a binary and a quaternary alloy, namely NiTi and NbMoTaW. In the case of the equi-atomic NiTi shape memory alloy, our attention focuses on designing a potential that properly captures its mechanical behavior, given that the existing potentials fail to predict elastic constants in agreement with experiments. To reach our aim, we included the stress tensors of different high temperature NiTi configurations in the fitting database. The obtained RF-MEAM potential outperforms existing EAM and MEAM potentials in predicting the lattice and elastic constants of austenitic and martensitic phases as well as the corresponding transformation temperatures. To demonstrate the suitability of this methodology also for more complex systems, a RF-MEAM potential is fitted to model the multi-component NbMoTaW high-entropy alloy. Validation is achieved through comparison between observables obtained through the MD output and ab initio data. The article also reports key improvements to the optimization code MEAMfit v2 and the freely-available LAMMPS implementation of the RF-MEAM formalism. Most notably, resorting to analytic derivatives of the objective function with respect to the potential parameters rather than derivatives through finite differences, the time necessary for fitting has decreased by an order of magnitude.},
keywords = {interatomic potential fitting, Molecular dynamics, multi-component alloy, nickel titanium, Phase transformation, reference-free MEAM},
pubstate = {published},
tppubtype = {article}
}
One of the effective potentials that has proven to be very versatile and useful for describing metals is the modified embedded atom method (MEAM) potential. The reference-free version of the MEAM (RF-MEAM) potential provides more flexibility for fitting than the 2NN-MEAM because it also describes the pair potential as an explicit function. In this work, we present a methodology to fit RF-MEAM potentials to DFT data. We then evaluate the performance of the fitted potential by comparing MD simulations with experimental and DFT data. As an example, the methodology is applied to a binary and a quaternary alloy, namely NiTi and NbMoTaW. In the case of the equi-atomic NiTi shape memory alloy, our attention focuses on designing a potential that properly captures its mechanical behavior, given that the existing potentials fail to predict elastic constants in agreement with experiments. To reach our aim, we included the stress tensors of different high temperature NiTi configurations in the fitting database. The obtained RF-MEAM potential outperforms existing EAM and MEAM potentials in predicting the lattice and elastic constants of austenitic and martensitic phases as well as the corresponding transformation temperatures. To demonstrate the suitability of this methodology also for more complex systems, a RF-MEAM potential is fitted to model the multi-component NbMoTaW high-entropy alloy. Validation is achieved through comparison between observables obtained through the MD output and ab initio data. The article also reports key improvements to the optimization code MEAMfit v2 and the freely-available LAMMPS implementation of the RF-MEAM formalism. Most notably, resorting to analytic derivatives of the objective function with respect to the potential parameters rather than derivatives through finite differences, the time necessary for fitting has decreased by an order of magnitude.
2018
2.
Srinivasan, Prashanth, Nicola, L., Simone, A.
Atomistic modeling of the orientation-dependent pseudoelasticity in NiTi: Tension, compression, and bending Journal Article
In: COMPUTATIONAL MATERIALS SCIENCE, vol. 154, pp. 25–36, 2018.
Abstract | BibTeX | Tags: Molecular dynamics, Phase transformation, Pseudoelasticity, Shape-memory alloy | Links:
@article{Srinivasan2018,
title = {Atomistic modeling of the orientation-dependent pseudoelasticity in NiTi: Tension, compression, and bending},
author = {Prashanth Srinivasan and L. Nicola and A. Simone},
doi = {10.1016/j.commatsci.2018.07.028},
year = {2018},
date = {2018-01-01},
journal = {COMPUTATIONAL MATERIALS SCIENCE},
volume = {154},
pages = {25–36},
publisher = {Elsevier B.V.},
abstract = {Pseudoelasticity in NiTi shape memory alloy single crystals depends on the loading direction. Here, we present a comprehensive study in which molecular dynamics simulations of austenitic bulk single crystals under strain-controlled tensile and compressive loading along the <110>, <111> and <100> directions are performed, and the mechanical response of the crystals are contrasted. All simulations are performed using the MEAM interatomic potential proposed by Ko et al. (2015). The transformation strains and the Young’s modulus of the initial austenitic and the final martensitic phases are compared with values obtained from the lattice deformation model and experimental results from the literature. Results show that depending on orientation the transformation occurs either through the formation of martensitic Lüders bands or through the transient formation of a multivariant martensite which, upon reorientation, becomes a dominant final single variant.
Simulations are also performed to assess the orientation-dependent behavior of nano-wires subjected to bending, since the flexibility of the wires is orientation dependent.},
keywords = {Molecular dynamics, Phase transformation, Pseudoelasticity, Shape-memory alloy},
pubstate = {published},
tppubtype = {article}
}
Pseudoelasticity in NiTi shape memory alloy single crystals depends on the loading direction. Here, we present a comprehensive study in which molecular dynamics simulations of austenitic bulk single crystals under strain-controlled tensile and compressive loading along the <110>, <111> and <100> directions are performed, and the mechanical response of the crystals are contrasted. All simulations are performed using the MEAM interatomic potential proposed by Ko et al. (2015). The transformation strains and the Young’s modulus of the initial austenitic and the final martensitic phases are compared with values obtained from the lattice deformation model and experimental results from the literature. Results show that depending on orientation the transformation occurs either through the formation of martensitic Lüders bands or through the transient formation of a multivariant martensite which, upon reorientation, becomes a dominant final single variant.
Simulations are also performed to assess the orientation-dependent behavior of nano-wires subjected to bending, since the flexibility of the wires is orientation dependent.
Simulations are also performed to assess the orientation-dependent behavior of nano-wires subjected to bending, since the flexibility of the wires is orientation dependent.
2017
1.
Srinivasan, Prashanth, Nicola, L., Simone, A.
Modeling pseudo-elasticity in NiTi: Why the MEAM potential outperforms the EAM-FS potential Journal Article
In: COMPUTATIONAL MATERIALS SCIENCE, vol. 134, pp. 145–152, 2017.
Abstract | BibTeX | Tags: Molecular dynamics, Phase transformation, Pseudo-elasticity, Shape memory alloy | Links:
@article{Srinivasan2017,
title = {Modeling pseudo-elasticity in NiTi: Why the MEAM potential outperforms the EAM-FS potential},
author = {Prashanth Srinivasan and L. Nicola and A. Simone},
doi = {10.1016/j.commatsci.2017.03.026},
year = {2017},
date = {2017-01-01},
journal = {COMPUTATIONAL MATERIALS SCIENCE},
volume = {134},
pages = {145–152},
publisher = {Elsevier B.V.},
abstract = {A comparison of the EAM-Finnis-Sinclair and the MEAM potential, two of the recently developed potentials to model NiTi, is carried out. The potentials are compared by studying the pseudo-elastic behavior in bulk NiTi for one specific crystallographic orientation. To this end we perform, for the first time, simulations where the transformation occurs not only under compressive but also under tensile loading along < 100 >(B2) using both potentials. Results indicate that in both cases the MEAM potential captures the pseudo-elastic behavior more accurately. By using a lattice deformation model, it is demonstrated that the inaccurate transformation strains predicted by the EAM-Finnis-Sinclair potential are a direct consequence of its inability to predict experimental values of the lattice constants. Similarly, it is shown that the more precise values of the Young's modulus of the initial austenitic and the final martensitic phase estimated by the MEAM potential are the result of its ability to predict elastic constants more accurately than the EAM-Finnis-Sinclair potential. As a result, it is concluded that the MEAM potential is better suited to study the overall pseudo-elastic behavior in NiTi.},
keywords = {Molecular dynamics, Phase transformation, Pseudo-elasticity, Shape memory alloy},
pubstate = {published},
tppubtype = {article}
}
A comparison of the EAM-Finnis-Sinclair and the MEAM potential, two of the recently developed potentials to model NiTi, is carried out. The potentials are compared by studying the pseudo-elastic behavior in bulk NiTi for one specific crystallographic orientation. To this end we perform, for the first time, simulations where the transformation occurs not only under compressive but also under tensile loading along < 100 >(B2) using both potentials. Results indicate that in both cases the MEAM potential captures the pseudo-elastic behavior more accurately. By using a lattice deformation model, it is demonstrated that the inaccurate transformation strains predicted by the EAM-Finnis-Sinclair potential are a direct consequence of its inability to predict experimental values of the lattice constants. Similarly, it is shown that the more precise values of the Young's modulus of the initial austenitic and the final martensitic phase estimated by the MEAM potential are the result of its ability to predict elastic constants more accurately than the EAM-Finnis-Sinclair potential. As a result, it is concluded that the MEAM potential is better suited to study the overall pseudo-elastic behavior in NiTi.
