Mapping the structural–mechanical landscape of amorphous carbon with ReaxFF molecular dynamics
Year: 2025
Type: article
Abstract: We use ReaxFF molecular dynamics (MD) to investigate the relationship between structural and mechanical properties in bulk and nanostructured amorphous carbon (a-C). The liquid-quench MD method is used to generate isotropic bulk samples with mass densities ranging from 0.96 to 3.29 g/cm3. Structural analysis identifies two types of structures with distinct short- and medium-range order: lower-density sp2-dominated a-C, which is characterized by a bimodal ring-size distribution, and higher-density sp3-dominated tetrahedral amorphous carbon (ta-C), exhibiting a unimodal ring-size distribution. Stress–strain MD simulations and analysis reveal how an atomistic structure impacts elastic properties and post-yield atomic rearrangements. All stretched structures demonstrate elastic isotropy and plasticity driven by a ring-size expansion mechanism reflected in changes in ring statistics. The plastic region is substantially larger in ta-C than in a-C due to the post-yield shift from sp3 to sp2 C dominant bonding. In both a-C and ta-C, ultimate failure occurs when a reactive crack, traversed by long sp chains, forms and propagates predominantly perpendicular to the direction of the applied strain. Oxygen infiltration into the fractured region significantly reduces stress resistance, primarily through the early rupture of long sp chains. MD simulations and analysis are extended to a-C slabs, a-C nanotubes, and partially a-C nanotubes. The latter nanostructure highlights the differences between the elastically isotropic a-C walls, which develop circumferential cracking, and the crystalline walls, which tear along crystallographic directions. These results provide a strong foundation for further computational characterization of a-C materials.
Source: Journal of Applied Physics
DOI: 10.1063/5.0246126
Language: English
Subfield: Materials Chemistry
Field: Materials Science
Domain: Physical Sciences
Open Access status: hybrid
Estimated APC paid: $3,500
Awards: G1335864876, THE INSTITUTE FOR ULTRA-STRONG COMPOSITES BY COMPUTATIONAL DESIGN (US-COMP) WILL BE FOCUSED ON THE MODELING-DRIVEN DESIGN OF A NEW CLASS OF ULTRA-HIGH-STRENGTH-LIGHTWEIGHT (UHSL) MATERIALS FOR FUTURE MANNED MARS MISSIONS. THESE MATERIALS WILL MEET THE REQUIRED MECHANICAL PERFORMANCE GOALS SET FORTH BY NASA AND EXCEED THOSE EXHIBITED BY CURRENT STATE-OF-THE-ART CARBON-FIBER COMPOSITES. US-COMP S VISION IS TO SERVE AS A FOCAL POINT FOR PARTNERSHIPS BETWEEN NASA OTHER AGENCIES INDUSTRY AND ACADEMIA TO: (1) ENABLE COMPUTATIONALLY-DRIVEN DEVELOPMENT OF CARBON NANOTUBE (CNT)-BASED UHSL STRUCTURAL MATERIALS AND (2) EXPAND THE RESOURCE OF HIGHLY SKILLED ENGINEERS SCIENTISTS AND TECHNOLOGISTS IN THIS EMERGING FIELD TO ENHANCE THE U.S. LEADERSHIP IN CRITICAL LIGHTWEIGHT STRUCTURAL MATERIALS. THIS VISION WILL BE ACHIEVED THROUGH THE FOUR PRINCIPLE OBJECTIVES: ESTABLISH A NEW COMPUTATIONALLY-DRIVEN MATERIAL DESIGN PARADIGM FOR RAPID MATERIAL DEVELOPMENT AND DEPLOYMENT DEVELOP A NOVEL UHSL STRUCTURAL MATERIAL FOR USE IN DEEP SPACE EXPLORATION. THE PANEL-LEVEL TESTS AND DEMONSTRATION OF THE NOVEL MATERIALS WILL BE CARRIED OUT TO MOVE THE DEVELOPED TECHNOLOGY TO A TECHNICAL READINESS LEVEL (TRL) OF 4. DEVELOP NOVEL MODELING PROCESSING AND TESTING TOOLS AND METHODS FOR CNT-BASED COMPOSITE MATERIALS ESTABLISH A POOL OF HIGHLY SKILLED ENGINEERS AND SCIENTISTS TO CONTRIBUTE TO THE MATERIALS DEVELOPMENT WORKFORCE. AN INTERDISCIPLINARY AND DIVERSE TEAM OF RESEARCHERS FROM ACADEMIA INDUSTRY AND NATIONAL LABS WILL PARTICIPATE IN THE PROJECT. THE COMPUTATIONAL DESIGN OF THE MATERIAL WILL BE DRIVEN BY A MODELING EFFORT TO INTEGRATE TOPOLOGICAL OPTIMIZATION ATOMISTIC MODELING MOLECULAR MODELING MESOSCALE MODELING AND CONTINUUM-BASED COMPUTATIONAL MECHANICS. INNOVATIONS IN MATERIALS SYNTHESIS AND MANUFACTURING TECHNIQUES WILL ENSURE THE PERFORMANCE AND SCALE-UP FABRICATION OF AEROSPACE-QUALITY TEST SAMPLES AND PANELS. MULTISCALE TESTING AND CHARACTERIZATION CAPABILITIES WILL BE ESTABLISHED AND INTEGRATED TO VALIDATE THE MODELING AND MANUFACTURING EFFORTS AND TO COMPLETE THE PROOF-OF-CONCEPT CYCLE. PARTICIPATION OF THE INDUSTRIAL PARTNERS WILL PROVIDE AND ENSURE THE SCALABILITY AND AEROSPACE-GRADE QUALITY OF THE DEVELOPED COMPOSITE MATERIAL. THE DEVELOPED MATERIALS AND MATERIALS DEVELOPMENT METHODS WILL HAVE A MAJOR IMPACT ON THE AEROSPACE COMMUNITY. FIRST UHSL MATERIALS WILL BE DEVELOPED WITH THE RIGOROUS STRENGTH MODULUS AND FRACTURE TOUGHNESS PROPERTIES NECESSARY FOR MANNED MARS MISSIONS. SECOND A NEW COMPUTATIONALLY-DRIVEN MATERIALS DESIGN PARADIGM WILL BE ESTABLISHED TO DEVELOP THE UHSL MATERIAL OF INTEREST AND FOR FUTURE RAPID MATERIALS DESIGN AND DEVELOPMENT EFFORTS. THIRD A FUNDAMENTAL UNDERSTANDING OF LOAD TRANSFER AND MULTISCALE FAILURE MECHANISMS OF CNT-BASED COMPOSITE MATERIALS WILL BE ESTABLISHED TO ACHIEVE THEIR THEORETICAL PERFORMANCE. FOURTH A REPRODUCIBLE ENGINEERING PERFORMANCE DATA FROM AEROSPACE-QUALITY AND SCALE-UP PANEL TEST RESULTS BUILDING UPON AEROSPACE-GRADE RESIN SYSTEMS AND HIGH-QUALITY COMMERCIALLY AVAILABLE CNT MATERIALS TO ENSURE SCALABILITY TO CONDUCT ASTM STANDARD TESTS. ANOTHER IMPORTANT EMPHASIS OF THE INSTITUTE WILL BE IN WORKFORCE DEVELOPMENT. STUDENTS WILL BE TRAINED FOR DEVELOPING AND UTILIZING ADVANCED COMPUTATIONAL AND EXPERIMENTAL APPROACHES FOR LIGHTWEIGHT MATERIALS. FUNDS WILL BE RESERVED FOR THE STUDENTS TO HAVE EXTENDED VISITS TO NASA FACILITIES DURING SUMMER MONTHS FOR DIRECT MENTORSHIP BY NASA RESEARCHERS. THESE ACTIVITIES WILL STRENGTHEN THE PARTNERSHIPS BETWEEN THE INSTITUTE MEMBERS AND NASA. WITH THE HELP OF THE HBCU PARTICIPANT (FLORIDA A&M UNIVERSITY) THE INSTITUTE WILL ESTABLISH A DIVERSE GROUP OF BOTH RESEARCHERS AND GRADUATE STUDENTS., EXPERIMENTAL IDENTIFICATION AND ATOMISTIC SIMULATIONS OF ACTIVE SITES, RATES AND REACTION EXTENT IN THERMO-CATALYTIC DECOMPOSITION AND REGENERATION TOWARDS MAINTAINING AUTOCATALYTIC ACTIVITY, MIP: 2D Crystal Consortium (MIP-2DCC), G3829267213, G4653638168
OpenAlex ID: W4407413855