Elastocaloric Effect in Graphene Kirigami

Kirigami, a traditional Japanese art of paper-cutting, has recently been explored for its elastocaloric effect (ECE) in kirigami-based materials (KMs), where applying strain induces temperature changes. In this study, we investigate the ECE in a nanoscale graphene kirigami (GK) monolayer, representing the thinnest possible KM, to better understand this phenomenon. Through molecular dynamics simulations, we analyze the temperature change and coefficient of performance (COP) of the nanoscale GK architecture. Our findings reveal that while GKs lack the intricate temperature changes observed in macroscopic KMs, they exhibit a substantial temperature change of approximately 9.32 K (23 times higher than that of macroscopic KMs, which is about 0.4K) for heating and -3.50 K for cooling. Additionally, they demonstrate reasonable COP values of approximately 1.57 and 0.62, respectively. It is noteworthy that the one-atom-thick graphene configuration prevents the occurrence of the complex temperature distribution observed in macroscopic KMs.Comment: 14 pages, 06 figures, and 01 tabl

Predicting Psi-BN: computational insights into its mechanical, electronic, and optical characteristics

Computational materials are pivotal in advancing our understanding of distinct material classes and their properties, offering valuable insights in predicting novel structures and complementing experimental approaches. In this context, Psi-graphene is a stable two-dimensional carbon allotrope composed of 5-6-7 carbon rings theoretically predicted recently. Using density functional theory (DFT) calculations, we explored its boron nitride counterpart's mechanical, electronic, and optical characteristics (Psi-BN). Our results indicate that Psi-BN possesses a band gap of 4.59 eV at the HSE06 level. Phonon calculations and ab initio molecular dynamics simulations demonstrated that this material has excellent structural and dynamic stability. Moreover, its formation energy is -7.48 eV. Psi-BN exhibited strong ultraviolet activity, suggesting its potential as an efficient UV collector. Furthermore, we determined critical mechanical properties of Psi-BN, such as the elastic stiffness constants, Young's modulus (250-300 GPa), and Poisson ratio (0.7), providing valuable insights into its mechanical behavior.Comment: 13 pages, 7 figure

TODD-Graphene: A Novel Porous 2D Carbon Allotrope for High-Performance Lithium-Ion Batteries

The class of 2D carbon allotropes has garnered significant attention due to its exceptional optoelectronic and mechanical properties, crucial for diverse device applications, such as energy storage. This study employs density functional theory calculations, ab initio molecular dynamics (AIMD), and classical reactive (ReaxFF) molecular dynamics (MD) simulations to introduce TODD-Graphene, a novel 2D planar carbon allotrope with a porous structure composed of 3-8-10-12 carbon rings. TODD-G exhibits intrinsic metallic properties with low formation energy and demonstrates exceptional dynamic, thermal, and mechanical stability. Calculations reveal a high theoretical capacity for adsorbing Li atoms by showing a low average diffusion barrier of 0.83 eV and a metallic framework boasting excellent conductivity, emerging as a promising anode material for lithium-ion batteries. We also calculated the charge carrier mobility for electrons and holes in TOOD-G, and the values surpassed the graphene ones. Classical reactive MD simulation results suggested its structural integrity with no bond reconstructions at 1800 K.Comment: 21 pages, 11 figure

Sun-Graphyne: A New 2D Carbon Allotrope with Dirac Cones

Due to the success achieved by graphene, several 2D carbon-based allotropes were theoretically predicted and experimentally synthesized. Here, we propose a new 2D carbon allotrope named Sun-Graphyne (S-GY). We used density functional theory and reactive molecular dynamics simulations to investigate its mechanical, structural, electronic, and optical properties. The results showed that S-GY exhibits good dynamical and thermal stabilities. Its formation energy and elastic moduli are -8.57 eV/atom and 262.37 GPa, respectively. S-GY is a semi-metal and presents two Dirac cones in its band structure. This material is transparent, and its intense optical activity is limited to the infrared region. Remarkably, the band structure of S-GY remains practically unchanged at even moderate strain regimes. As far as we know, this is the first 2D carbon allotrope to exhibit this behaviour.Comment: 17 pages, and 11 figure

Características tecnológicas da fibra do algodão herbáceo em resposta a irrigação.

O objetivo deste trabalho foi avaliar o efeito da aplicação de lâminas de irrigação (474,7; 405,2; 360,2 e 315,2 mm) sobre as características tecnológicas da fibra do algodão herbáceo (comprimento de fibra, uniformidade de comprimento de fibra, índice de fiabilidade, índice de fibras curtas, resistência, índice micronaire, maturidade e porcentagem de fibras). O experimento foi conduzido na área experimental da Embrapa Meio-Norte, em Teresina, PI. As lâminas de irrigação, repostas com base na evapotranspiração de referência (ETo) local, foram aplicadas através de um sistema de irrigação por aspersão convencional. O delineamento experimental utilizado foi de blocos casualizados, com quatro repetições e as lâminas dispostas em faixas. O comprimento de fibra (UHM), índice de uniformidade do comprimento da fibra (UNF) e o índice de fiabilidade (SCI) apresentaram comportamento linear crescente com a imposição de lâminas de irrigação. O índice de fibras curtas (SFI), o índice micronaire (MIC) e a maturidade (MAT) decresceram linearmente com o acréscimo das lâminas de irrigação. A porcentagem da fibra (PF) seguiu comportamento quadrático em função das lâminas de irrigação, alcançando o valor máximo (42,79%) com a lâmina ótima de irrigação de 397,3 mm. A resistência (STR), não foi influenciada de maneira significativa com a aplicação das diferentes lâminas de irrigação

Coeficientes de cultura do algodão herbáceo e do feijão-caupi em sistemas monocultivo e consorciado.

O conhecimento sobre a demanda hídrica das espécies vegetais, cultivadas em sistema monocultivo e/ou consorciado, é essencial para que se mantenham os níveis de água no solo em condições de atendimento às suas necessidades hídricas. O trabalho teve por objetivo determinar os coeficientes de cultura (Kc?s) do cultivar de algodão herbáceo (Gossypium hirsutum L.), BRS Camaçari e do cultivar de feijão-caupi (Vigna unguiculata (L.) Walp.), BRS Guariba, em sistemas monocultivo e consorciado e em seus diversos estádios de desenvolvimento. O experimento foi conduzido na área experimental da Embrapa Meio-Norte, em Teresina, PI. Em sistema monocultivo, os Kc?s médios encontrados para o algodão herbáceo apresentam valores de 0,39 a 1,16, com o valor máximo aos 57 dias após a semeadura. O Kc do algodão, em consórcio com o feijão-caupi, apresenta o valor mínimo de 0,53 e máximo de 1,34, aos 55 dias após a semeadura. O feijão-caupi, em monocultivo, apresenta valor mínimo de Kc igual a 0,45 e máximo de 1,13, aos 50 dias após a semeadura

Supporting emergence or reference drought tolerance phenotyping centers - drought phenotyping network.

The project developed and made useful phenotypic evaluation protocols for cereals (maize, sorghum, rice, and wheat) and legume crops (common bean and cowpea), and established phenotyping site specific experimental (SSE) areas of excellence (2) and reference (5) for drought tolerance (DT) studies according to specific climatic condition, soil physical and chemical properties, with laboratories, controlled environment target fields and greenhouses, training unit for researchers and assistants, with facilities and well defined dry season periods to assure total irrigation and soil moisture control during the drought phenotyping field trials. Overall, the project established a scientific and service network for drought tolerance phenotyping in Brazil