We introduce a model AFM tip/substrate system that includes full atomistic detail as well as system compliance to study the transitions between three regimes of atomic friction: smooth sliding, stick-single slip, and stick-multiple slip. We characterize these atomic friction regimes in terms of static and dynamic effects, and investigate how the slip modes affect the mean friction. Molecular st...

Molecular dynamics (MD) methods are opening new opportunities for simulating the fundamental processes of material behavior at the atomistic level. However, current analysis is limited to small domains and increasing the size of the MD domain quickly presents intractable computational demands. A preferred approach to surmount this computational limitation has been to combine continuum mechanics...

Abstract. We give a goal-oriented a posteriori error estimator for the atomistic-continuum modeling error in the quasicontinuum method, and we use this estimator to design an adaptive algorithm to compute a quantity of interest to a given tolerance by using a nearly minimal number of atomistic degrees of freedom. We present computational results that demonstrate the effectiveness of our algorit...

Involved in various neurodegenerative diseases, amyloid fibrils and plaques feature a hierarchical structure, ranging from the atomistic to the micrometer scale. At the atomistic level, a dense and organized hydrogen bond network is resembled in a beta-sheet rich secondary structure, which drives a remarkable stiffness in the range of 10–20 GPa, larger than many other biological nanofibrils, a ...

The polyamidoamide (PAMAM) class of dendrimers was one of the first dendrimers synthesized by Tomalia and co-workers at Dow. Since its discovery the PAMAMs have stimulated many discussions on the structure and dynamics of such hyperbranched polymers. Many questions remain open because the huge conformation disorder combined with very similar local symmetries have made it difficult to characteri...

Direct atomistic simulations of dislocation multiplication in fcc aluminum reveal an unexpected mechanism, in which a Frank-Read source emits dislocations with Burgers vectors different from that of the source itself. The mechanism is traced to a spontaneous nucleation of partial dislocation loops within the stacking fault. Understanding and a quantitative description of this unusual process ar...

The aim of this paper is to provide a simulation strategy to study the liquid-solid transition of triglycerides. The strategy is based on a multiscale approach. A coarse-grained model, parameterized on the basis of reference atomistic simulations, has been used to model the liquid-solid transition. A reverse mapping procedure has been proposed to reconstruct atomistic models from coarse-grained...

Finite Element Analysis (FEA) and atomistic simulations are used to model Ge/Si quantum dots. The three dimensional non-uniform composition profile in Ge(Si)/Si(001) quantum dots is calculated using atomistic modelling. The results are compared to experimental data from the literature. FEA is used to model the contact angle dependence of the strain energy of the QD. An equation is fitted to the...