Optical and Elastic Properties of Diamond-like Carbon with Metallic Inclusions: a Theoretical Study

A tough material commonly used in coatings is diamond-like carbon (DLC), that is, amorphous carbon with content in four-fold coordinated C higher than ∼70, and its composites with metal inclusions. This study aims to offer useful guidelines for the design and development of metal-containing DLC coatings for solar collectors, where the efficiency of the collector depends critically on the performance of the absorber coating. We use first-principles calculations based on density functional theory to study the structural, electronic, optical, and elastic properties of DLC and its composites with Ag and Cu inclusions at 1.5 and 3.0 atomic concentration, to evaluate their suitability for solar thermal energy harvesting. We find that with increasing metal concentration optical absorption is significantly enhanced while at the same time, the composite retains good mechanical strength: DLC with 70-80 content in four-fold coordinated C and small metal concentrations (3 at. ) will show high absorption in the visible (absorption coefficients higher than 10 5 cm-1) and good mechanical strength (bulk and Youngs modulus higher than 300 and 500 GPa, respectively)

First-principles study of coupled effect of ripplocations and S-vacancies in MoS 2

Sensoy, Mehmet Gokhan/0000-0003-4815-8061; Shirodkar, Sharmila N/0000-0002-9040-5858; Tritsaris, Georgios/0000-0002-5738-4493WOS: 000483884600020Recent experiments have revealed ripplocations, atomic-scale ripplelike defects on samples of MoS2 flakes. We use quantum mechanical calculations based on density functional theory to study the effect of ripplocations on the structural and electronic properties of single-layer MoS2, and, in particular, the coupling between these extended defects and the most common defects in this material, S-vacancies. We find that the formation of neutral S-vacancies is energetically more favorable in the ripplocation. in addition, we demonstrate that ripplocations alone do not introduce electronic states into the intrinsic bandgap, in contrast to S-vacancies. We study the dependence of the induced gap states on the position of the defects in the ripplocation, which has implications for the experimental characterization of MoS2 flakes and the engineering of quantum emitters in this material. Our specific findings collectively aim to provide insights into the electronic structure of experimentally relevant defects in MoS2 and to establish structure-property relationships for the design of MoS2-based quantum devices. Published under license by AIP Publishing.ARO MURIMURI [W911NF14-0247]; DOE BES AwardUnited States Department of Energy (DOE) [DE-SC0019300]; National Science Foundation (NSF)National Science Foundation (NSF) [ACI-1053575]The authors would like to thank Venkataraman Swaminathan and Daniel Larson for helpful discussions. S.S. acknowledges support by the ARO MURI (Award No. W911NF14-0247). This work was supported by the DOE BES Award No. DE-SC0019300. For calculations, computational resources were used on the Odyssey cluster, which is maintained by the FAS Research Computing Group at Harvard University, and the Extreme Science and Engineering Discovery Environment (XSEDE), which is supported by the National Science Foundation (NSF) under Grant No. ACI-1053575

First-principles study of coupled effect of ripplocations and S-vacancies in MoS2

Sensoy, Mehmet Gokhan/0000-0003-4815-8061; Shirodkar, Sharmila N/0000-0002-9040-5858; Tritsaris, Georgios/0000-0002-5738-4493WOS: 000483884600020Recent experiments have revealed ripplocations, atomic-scale ripplelike defects on samples of MoS2 flakes. We use quantum mechanical calculations based on density functional theory to study the effect of ripplocations on the structural and electronic properties of single-layer MoS2, and, in particular, the coupling between these extended defects and the most common defects in this material, S-vacancies. We find that the formation of neutral S-vacancies is energetically more favorable in the ripplocation. in addition, we demonstrate that ripplocations alone do not introduce electronic states into the intrinsic bandgap, in contrast to S-vacancies. We study the dependence of the induced gap states on the position of the defects in the ripplocation, which has implications for the experimental characterization of MoS2 flakes and the engineering of quantum emitters in this material. Our specific findings collectively aim to provide insights into the electronic structure of experimentally relevant defects in MoS2 and to establish structure-property relationships for the design of MoS2-based quantum devices. Published under license by AIP Publishing.ARO MURIMURI [W911NF14-0247]; DOE BES AwardUnited States Department of Energy (DOE) [DE-SC0019300]; National Science Foundation (NSF)National Science Foundation (NSF) [ACI-1053575]The authors would like to thank Venkataraman Swaminathan and Daniel Larson for helpful discussions. S.S. acknowledges support by the ARO MURI (Award No. W911NF14-0247). This work was supported by the DOE BES Award No. DE-SC0019300. For calculations, computational resources were used on the Odyssey cluster, which is maintained by the FAS Research Computing Group at Harvard University, and the Extreme Science and Engineering Discovery Environment (XSEDE), which is supported by the National Science Foundation (NSF) under Grant No. ACI-1053575

Diffusion of Lithium in Bulk Amorphous Silicon: A Theoretical Study

The rate performance of lithium-ion secondary batteries depends critically on the kinetic transport of Li within the anode material. Here we use first-principles theoretical calculations to study the diffusion of Li in the low-concentration limit, using model electrodes of crystalline and four-fold coordinated bulk amorphous silicon. We identify Li diffusion pathways that have relatively low energy barriers (<0.50 eV) in amorphous silicon and discuss how diffusion at short (∼2.5 Å), intermediate (∼10 Å), and long (>1 nm) distances depends on the atomic-scale features of the silicon host. We find that both the energy barriers for diffusion and the topology of the atomic structure control the diffusion. We estimate the diffusion rate in amorphous Si anode to be comparable to the rate in crystalline Si anodes. These findings shed light on the wide range of reported experimental results for Li diffusion in Si anodes