第一性原理计算在相图计算中的应用研究进展

相图计算 （Calculation of Phase Diagram, CALPHAD)是冶金 、化工 、材料设计等各个领域的重要研究工具,随着传统材料体系的研究深入和新材料体系的不断被发现,相关的相图和热力学实验数据愈显匮乏.基于电子层面的第一性原理计算（First-principles Calculations),可以从体系基态性质出发,研究亚稳相、金属间化合物的结构、合金的稳定性,促进 CALPHAD 的发展.文中关注了近年来第一性原理计算在 CALPHAD 技术当中的应用研究进展,从计算化合物的能量性质,相图,动力学性质等方面进行系统阐述.      

相图计算研究的进展

相图计算作为材料设计的一部分受到了人门更多的重视.本文概述了相图计算的优点,简要评述了相图计算方法的发展现状和前沿研究,着重强调了将第一性原理计算和相图计算方法相结合以及基于相图计算热力学数据库预测体系物理性质对于材料设计和冶金过程优化的重要性.     

M-Si-B合金非晶形成能力的CALPHAD模式评估

Evaluation of the amorphous-forming ability of M-Si-B ternary alloys using CALPHAD approach@長谷部光弘$日本九州工业大学 @OHTANI Hiroshi$Department of Materials Science and Engineering, Kyushu Institute of Technology @HASEBE Mitsuhiro$Department of Materials Science and Engineering, Kyushu Institute of Technology…     

镍铬轴承合金固溶时效态组织特征与力学性能

研究了00Cr40Ni55Al3Ti轴承合金固溶态和时效态的组织特征及硬度变化规律。结果表明:随着固溶温度的升高,α-Cr相析出数量呈下降趋势,在1 200℃时α-Cr相尺寸最小,面积分数仅为8.45%;高于1 200℃时,α-Cr相尺寸逐渐增大,数量减少。固溶处理后冷却速度越快,α-Cr相析出数量越少,硬度降低;固溶温度在1 190～1 210℃之间以138℃/s进行冷却,经600℃×6 h时效处理后,硬度超过59.7HRC,合金微观组织主要由球状α-Cr相和均匀片层组织及弥散分布其中的纳米级γ′相组成,硬度较为均匀。1 200℃固溶处理以138℃/s进行冷却,经550℃保温6 h后,00Cr40Ni55Al3Ti合金显微组织为球状α-Cr相、片层组织和非片层组织,非片层组织面积分数约为32.21%,片层组织硬度达703HV,非片层组织硬度为249HV;当时效温度为600和650℃时,时效时间在5～7 h范围内,显微组织为均匀分布的片层组织和球状α-Cr相,硬度为676HV～712HV。00Cr40Ni55Al3Ti轴承合金在1 190～1 210℃之间进行固溶处理后快速冷却(冷却速...     

Computation of object approach by a wide-field, motion-sensitive neuron

The lobula giant motion detector (LGMD) in the locust visual system is a wide-field, motion-sensitive neuron that responds vigorously to objects approaching the animal on a collision course. We investigated the computation performed by LGMD when it responds to approaching objects by recording the activity of its postsynaptic target, the descending contralateral motion detector (DCMD). In each animal, peak DCMD activity occurred a fixed delay delta (15 相似文献   

A combined calorimetric and semiempirical quantum chemical approach to describe the solution thermodynamics of drugs

The present study aimed to compare the actions of the selective kappa opioid receptor agonist enadoline (CI-977) with morphine in order to see if there is a heterogeneity of opioid receptors between spinal reflex pathways. High (C- and A-fibre evoked activity) and low (A-fibres only) intensity electrical stimulation of dorsal roots in the neonatal rat hemisected spinal cord preparation in vitro was used to distinguish between synaptic activity measured in the corresponding ventral root. Enadoline selectively depressed the high intensity-evoked EPSP with an EC50 of 7.6 nM (n = 7), contrasting with our previous finding in this preparation that morphine is an equipotent depressant of A- and C-fibre-mediated synaptic responses. The depressant effects of enadoline and morphine were reversed by naloxone giving apparent Kd values of 14 +/- 3 nM (n = 4) for enadoline-induced and 4.2 +/- 1 nM (n = 4) for morphine-induced depression. These data suggest that activation of kappa opioid receptors has a selective depressant action on C-fibre-mediated synaptic activity. Such a functional difference mediated at a subclass of opioid receptors has not been previously observed in an in vitro spinal preparation.     

Stabilities,mechanical and thermodynamic properties of Al-RE intermetallics:A first-principles study

Stabilities,mechanical and thermodynamic properties of 87 intermetallics in Al-RE binary system were studied by first-principles based on density functional theory(DFT).The results show that the calculated stabilities at T=0 K are in good agreement with experimental values.Al2 RE intermetallics exhibit the best stability in Al-RE binary compounds;and the stabilities in descending order are Al2 RE,Al3 RE,AlRE,Al11RE₃,AlRE2 and AlRE₃.The calculated Al-RE intermetallics possess mechanical stabilities.The hardness and strength of the most Al-RE intermetallics are greater than pure aluminum except AlCe,AlPr,AlEu and AlYb.The hardness and strength in descending order are Al11RE₃,Al3 RE,Al2 RE and AIRE.Part of AlRE intermetallics exhibit ductility;the others are brittle.The heat capacities of Al-RE intermetallics in ascending order are Al-Sc,Al-Y,Al-lanthanides.On the contrary,the coefficient of thermal expansion(CTE)in ascending order is Al-lanthanides,Al-Y and Al-Sc.     

Stabilities,mechanical and thermodynamic properties of Al-RE intermetallics:A first-principles study

Stabilities,mechanical and thermodynamic properties of 87 intermetallics in Al-RE binary system were studied by first-principles based on density functional theory(DFT).The results show that the calculated stabilities at T=0 K are in good agreement with experimental values.Al2 RE intermetallics exhibit the best stability in Al-RE binary compounds;and the stabilities in descending order are Al2 RE,Al3 RE,AlRE,Al11RE₃,AlRE2 and AlRE₃.The calculated Al-RE intermetallics possess mechanical stabilities.The hardness and strength of the most Al-RE intermetallics are greater than pure aluminum except AlCe,AlPr,AlEu and AlYb.The hardness and strength in descending order are Al11RE₃,Al3 RE,Al2 RE and AIRE.Part of AlRE intermetallics exhibit ductility;the others are brittle.The heat capacities of Al-RE intermetallics in ascending order are Al-Sc,Al-Y,Al-lanthanides.On the contrary,the coefficient of thermal expansion(CTE)in ascending order is Al-lanthanides,Al-Y and Al-Sc.     

Computation of gas phase equilibria—a general algorithm using the Newton-Raphson method

A general algorithm is proposed that calculates complex gaseous equilibria using the Newton-Raphson method. The algorithm was tested on the C-H-O-S-N system and its sub-systems H-O, C-H-O, C-O-S, C-H-O-N, C-H-O-S and H-O-S-N. It converged in all regions of these systems when there were no condensed phases present. It was found that the algorithm was insensitive to initial estimates usually required when using the Newton-Raphson method.