Sandia National Laboratories

About: Sandia National Laboratories is a facility organization based out in Livermore, California, United States. It is known for research contribution in the topics: Laser & Combustion. The organization has 21501 authors who have published 46724 publications receiving 1484388 citations. The organization is also known as: SNL & Sandia National Labs.

Performance and Cost Assessment of Machine Learning Interatomic Potentials.

Abstract: Machine learning of the quantitative relationship between local environment descriptors and the potential energy surface of a system of atoms has emerged as a new frontier in the development of interatomic potentials (IAPs). Here, we present a comprehensive evaluation of machine learning IAPs (ML-IAPs) based on four local environment descriptors-atom-centered symmetry functions (ACSF), smooth overlap of atomic positions (SOAP), the spectral neighbor analysis potential (SNAP) bispectrum components, and moment tensors-using a diverse data set generated using high-throughput density functional theory (DFT) calculations. The data set comprising bcc (Li, Mo) and fcc (Cu, Ni) metals and diamond group IV semiconductors (Si, Ge) is chosen to span a range of crystal structures and bonding. All descriptors studied show excellent performance in predicting energies and forces far surpassing that of classical IAPs, as well as predicting properties such as elastic constants and phonon dispersion curves. We observe a general trade-off between accuracy and the degrees of freedom of each model and, consequently, computational cost. We will discuss these trade-offs in the context of model selection for molecular dynamics and other applications.

Hydrogen interactions with defects in crystalline solids

Abstract: Hydrogen interactions with imperfections in crystalline metals and semiconductors are reviewed. Emphasis is given to mechanistic experiments and theoretical advances contributing to predictive understanding. Important directions for future research are discussed.

Novel Powder-Processing Methods for Advanced Ceramics

Abstract: Novel approaches for optimized powder processing of advanced ceramics are reviewed with an emphasis on direct-casting methods and solid freeform fabrication techniques. The fundamental principles for green body formation are discussed; a distinction is made between physical and chemical gels based on the nature of the induced gelation. An overview of the properties of dense suspensions is presented, with a focus on the factors controlling the maximum solids loading. Recent work on direct measurements of interparticle forces in ceramic systems is presented and related to rheological properties.

Recent advances in single-asperity nanotribology

Abstract: As the size of electronic and mechanical devices shrinks to the nanometre regime, performance begins to be dominated by surface forces. For example, friction, wear and adhesion are known to be central challenges in the design of reliable micro- and nano-electromechanical systems (MEMS/NEMS). Because of the complexity of the physical and chemical mechanisms underlying atomic-level tribology, it is still not possible to accurately and reliably predict the response when two surfaces come into contact at the nanoscale. Fundamental scientific studies are the means by which these insights may be gained. We review recent advances in the experimental, theoretical and computational studies of nanotribology. In particular, we focus on the latest developments in atomic force microscopy and molecular dynamics simulations and their application to the study of single-asperity contact.