Entropy production in quasi-isentropic compression (QIC) is critically important for understanding the properties of materials under extremeconditions. However, the origin and accurate quantification of entropy in thi...Entropy production in quasi-isentropic compression (QIC) is critically important for understanding the properties of materials under extremeconditions. However, the origin and accurate quantification of entropy in this situation remain long-standing challenges. In this work, a framework is established for the quantification of entropy production and partition, and their relation to microstructural change in QIC. Cu50Zr50is taken as a model material, and its compression is simulated by molecular dynamics. On the basis of atomistic simulation-informed physicalproperties and free energy, the thermodynamic path is recovered, and the entropy production and its relation to microstructural change aresuccessfully quantified by the proposed framework. Contrary to intuition, entropy production during QIC of metallic glasses is relativelyinsensitive to the strain rate ˙γ when ˙γ ranges from 7.5 × 10^(8) to 2 × 10^(9)/s, which are values reachable in QIC experiments, with a magnitudeof the order of 10^(−2)kB/atom per GPa. However, when ˙γ is extremely high (>2 × 10^(9)/s), a notable increase in entropy production rate with˙γ is observed. The Taylor–Quinney factor is found to vary with strain but not with strain rate in the simulated regime. It is demonstrated thatentropy production is dominated by the configurational part, compared with the vibrational part. In the rate-insensitive regime, the increase inconfigurational entropy exhibits a linear relation to the Shannon-entropic quantification of microstructural change, and a stretched exponential relation to the Taylor–Quinney factor. The quantification of entropy is expected to provide thermodynamic insights into the fundamentalrelation between microstructure evolution and plastic dissipation.展开更多
Based on experimental results,this paper presents that under specificvibrational and solidifying conditions,there are several periodic layers appearing in thecrystallization of A1-3％ Mg alloy.The mechanism of the for...Based on experimental results,this paper presents that under specificvibrational and solidifying conditions,there are several periodic layers appearing in thecrystallization of A1-3％ Mg alloy.The mechanism of the formation of periodic layer isdiscussed.Furthermore,the use of the layers to identify the solid-liquid interface and theeffect of such layers on mechanical properties of alloy have been studied.展开更多
A model incorporating(Cs-A-ABAB)stacking with Cs atoms chemisorbed in hollow sites 2.70A above the top graphite plane and the two top graphite layers shear-shifted to AA stacking and expanded to a separation of 3.85A ...A model incorporating(Cs-A-ABAB)stacking with Cs atoms chemisorbed in hollow sites 2.70A above the top graphite plane and the two top graphite layers shear-shifted to AA stacking and expanded to a separation of 3.85A is the most reliable structure for Cs/graphite(0001)-(√3×√3)surfaces.The coexisting diffraction pattern including the diffraction ring and another set of (√3×√3) diffraction pattern which has a 30°rotation angle with respect to the normal(√3×√3)R3O°diffraction pattern could be explained.We consider this strueture to be in a prein ter cal ation state.展开更多
基金supported by the NSAF under Grant No.U1830206,the National Key R&D Program of China under Grant No.2017YFA0403200the National Natural Science Foundation of China under Grant Nos.11874424 and 12104507the Science and Technology Innovation Program of Hunan Province under Grant No.2021RC4026.
文摘Entropy production in quasi-isentropic compression (QIC) is critically important for understanding the properties of materials under extremeconditions. However, the origin and accurate quantification of entropy in this situation remain long-standing challenges. In this work, a framework is established for the quantification of entropy production and partition, and their relation to microstructural change in QIC. Cu50Zr50is taken as a model material, and its compression is simulated by molecular dynamics. On the basis of atomistic simulation-informed physicalproperties and free energy, the thermodynamic path is recovered, and the entropy production and its relation to microstructural change aresuccessfully quantified by the proposed framework. Contrary to intuition, entropy production during QIC of metallic glasses is relativelyinsensitive to the strain rate ˙γ when ˙γ ranges from 7.5 × 10^(8) to 2 × 10^(9)/s, which are values reachable in QIC experiments, with a magnitudeof the order of 10^(−2)kB/atom per GPa. However, when ˙γ is extremely high (>2 × 10^(9)/s), a notable increase in entropy production rate with˙γ is observed. The Taylor–Quinney factor is found to vary with strain but not with strain rate in the simulated regime. It is demonstrated thatentropy production is dominated by the configurational part, compared with the vibrational part. In the rate-insensitive regime, the increase inconfigurational entropy exhibits a linear relation to the Shannon-entropic quantification of microstructural change, and a stretched exponential relation to the Taylor–Quinney factor. The quantification of entropy is expected to provide thermodynamic insights into the fundamentalrelation between microstructure evolution and plastic dissipation.
文摘Based on experimental results,this paper presents that under specificvibrational and solidifying conditions,there are several periodic layers appearing in thecrystallization of A1-3％ Mg alloy.The mechanism of the formation of periodic layer isdiscussed.Furthermore,the use of the layers to identify the solid-liquid interface and theeffect of such layers on mechanical properties of alloy have been studied.
基金Project suported by the National Natural Science Foundation of China.
文摘A model incorporating(Cs-A-ABAB)stacking with Cs atoms chemisorbed in hollow sites 2.70A above the top graphite plane and the two top graphite layers shear-shifted to AA stacking and expanded to a separation of 3.85A is the most reliable structure for Cs/graphite(0001)-(√3×√3)surfaces.The coexisting diffraction pattern including the diffraction ring and another set of (√3×√3) diffraction pattern which has a 30°rotation angle with respect to the normal(√3×√3)R3O°diffraction pattern could be explained.We consider this strueture to be in a prein ter cal ation state.
