The accurate and efficient simulation of material systems with defects using atomistic-to-continuum (a/c) coupling methods is a significant focus in computational materials science. Achieving a balance between accurac...
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The accurate and efficient simulation of material systems with defects using atomistic-to-continuum (a/c) coupling methods is a significant focus in computational materials science. Achieving a balance between accuracy and computational cost requires the application of a posteriori error analysis and adaptive algorithms. In this paper, we provide a rigorous a posteriori error analysis for three common blended a/c methods: the blended energy-based quasi-continuum (BQCE) method, the blended force-based quasi-continuum (BQCF) method, and the atomistic/continuum blending with ghost force correction (BGFC) method. We discretize the Cauchy-Born model in the continuum region using first- and second-order finite element methods, with the potential for extending to higher-order schemes. The resulting error estimator provides both an upper bound on the true error and a reliable lower bound, subject to a controllable truncation term. Furthermore, we offer an a posteriori analysis of the energy error. We develop and implement an adaptive mesh refinement algorithm applied to two typical defect scenarios: a micro-crack and a Frenkel defect. In both cases, our numerical experiments demonstrate optimal convergence rates with respect to degrees of freedom, in agreement with a priori error estimates.
We formulate and analyze an optimization-based atomistic-to-continuum (AtC) coupling method for problems with point defects. Application of a potential-based atomistic model near the defect core enables accurate simul...
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We formulate and analyze an optimization-based atomistic-to-continuum (AtC) coupling method for problems with point defects. Application of a potential-based atomistic model near the defect core enables accurate simulation of the defect. Away from the core, where site energies become nearly independent of the lattice position, the method switches to a more efficient continuum model. The two models are merged by minimizing the mismatch of their states on an overlap region, subject to the atomistic and continuum force balance equations acting independently in their domains. We prove that the optimization problem is well-posed and establish error estimates.
We study the stability of ghost force-free energy-based atomistic-to-continuum (a/c) coupling methods. In one dimension we essentially complete the theory by introducing a universally stable a/c coupling as well as a ...
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We study the stability of ghost force-free energy-based atomistic-to-continuum (a/c) coupling methods. In one dimension we essentially complete the theory by introducing a universally stable a/c coupling as well as a stabilization mechanism for unstable coupling schemes. We then present a comprehensive study of a two-dimensional scalar planar interface setting, as a step towards a general two-dimensional/three-dimensional vectorial analysis. Our results point out various new challenges. For example, we find that none of the ghost force-free methods known to us is universally stable (i.e., stable under general interaction and general loads). We then explore to what extent our one-dimensional stabilization mechanism can be extended.
We consider the problem of a posteriori error estimates and adaptivity for three typical force-based atomistic-to-continuum coupling *** the residual and the stability estimates,we derive computable a posteriori error...
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We consider the problem of a posteriori error estimates and adaptivity for three typical force-based atomistic-to-continuum coupling *** the residual and the stability estimates,we derive computable a posteriori error estima-tors for the three methods in the energy norm and formulate adaptive algorithms using these *** numerical experiments show optimal convergence rates of these *** efficiency of the estimators are also demonstrated numerically.
We consider the a posteriori error estimation for an atomistic-to-continuum coupling scheme for a generic one-dimensional many-body next-nearest-neighbor interaction model in one dimension. We derive and rigorously pr...
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We consider the a posteriori error estimation for an atomistic-to-continuum coupling scheme for a generic one-dimensional many-body next-nearest-neighbor interaction model in one dimension. We derive and rigorously prove the efficiency of the residual type estimator. We prove the equivalence between the residual type and the gradient recovery-type estimator in the continuum region and propose a (novel) hybrid a posteriori error estimator by combining the two types of estimators. Our numerical experiments illustrate the optimal convergence rate of the adaptive algorithms using these estimators, whose effectivity indices are also presented.
In this work, we present a seamless, energy-conserving method to couple atomistic and continuum representations of a temperature field in a material. This technique allows a molecular dynamics simulation to be used in...
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In this work, we present a seamless, energy-conserving method to couple atomistic and continuum representations of a temperature field in a material. This technique allows a molecular dynamics simulation to be used in localized regions of the computational domain, surrounded and overlaid by a continuum finite element representation. Thermal energy can pass between the two regions in either direction, making larger simulations of nano-scale thermal processes possible. We discuss theoretical developments and numerical implementation details. In addition, we present and analyze a set of representative simulations. Published by Elsevier B.V.
We formulate a patch test consistent atomistic-to-continuum coupling (a/c) scheme that employs a second-order (potentially higher-order) finite element method in the material bulk. We prove a sharp error estimate in t...
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We formulate a patch test consistent atomistic-to-continuum coupling (a/c) scheme that employs a second-order (potentially higher-order) finite element method in the material bulk. We prove a sharp error estimate in the energy-norm, which demonstrates that this scheme is (quasi-) optimal amongst energy-based sharp-interface a/c schemes that employ the Cauchy-Born continuum model. Our analysis also shows that employing a higher-order continuum discretisation does not yield qualitative improvements to the rate of convergence.
A mathematical framework for the coupling of atomistic and continuum models by blending them over a subdomain subject to a constraint is developed. Using the framework, four classes of atomistic-to-continuum (AtC) ble...
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A mathematical framework for the coupling of atomistic and continuum models by blending them over a subdomain subject to a constraint is developed. Using the framework, four classes of atomistic-to-continuum (AtC) blending methods are established, their consistency is studied, and their relative merits are discussed. In addition, the framework helps clarify the origin of ghost forces and formalizes the notion of a patch test. Numerical experiments with the AtC methods are used to illustrate the theoretical results.
For a general class of atomistic-to-continuum coupling methods, coupling multi-body interatomic potentials with a P-1-finite element discretisation of Cauchy-Born nonlinear elasticity, this paper adresses the question...
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For a general class of atomistic-to-continuum coupling methods, coupling multi-body interatomic potentials with a P-1-finite element discretisation of Cauchy-Born nonlinear elasticity, this paper adresses the question whether patch test consistency (or, absence of ghost forces) implies a first-order error estimate. In two dimensions it is shown that this is indeed true under the following additional technical assumptions: (i) an energy consistency condition, (ii) locality of the interface correction, (iii) volumetric scaling of the interface correction, and (iv) connectedness of the atomistic region. The extent to which these assumptions are necessary is discussed in detail.
Several issues connected with bridging methods for atomistic-to-continuum(AtC)coupling are *** coupling approaches using various energy blending models are studied as well as the influence that model parameters,blendi...
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Several issues connected with bridging methods for atomistic-to-continuum(AtC)coupling are *** coupling approaches using various energy blending models are studied as well as the influence that model parameters,blending functions,and grids have on simulation *** use the Lagrange multiplier method for enforcing constraints on the atomistic and continuum displacements in the bridge *** also show that continuum models are not appropriate for dealing with problems with singular loads,whereas AtC bridging methods yield correct results,thus justifying the need for a multiscale *** investigate models that involve multiple-neighbor interactions in the atomistic region,particularly focusing on a comparison of several approaches for dealing with Dirichlet boundary conditions.
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