Man proposes, god disposes
谋事在人,成事在天
Updated time: 11/20 2024.
I. phase transition of Au thinfilm on silica substrate
0. Theory
1. Layer by layer transformation
- Ref: Layer-by-layer phase transformation in Ti3O5 revealed by machine-learning molecular dynamics simulations, NC
2. How to study the phase transition
- Energy difference (thickness/strain - film, Bain path/外延贝恩相变路径/静水压 - bulk)
- EOS
- Energy barrier (thickness - film，用什么方法去描述中间态，驱动力)
- Surface energy
3. Energy compare
DFT -> lattice constant is same as the experiment.
Bulk: SiO2, FCC, HCP
Film: FCC, HCP
On substrate: FCC/HCP/more layers/more sustrates
Moleculars: H2O2, … etc
Focused items: total energy, adsorb energy, interface energy, surface energy
4. Electronic structure
- EOS: Theoretical prediction of a phase transition in gold
5. Other properties
6. Path
Bain path
surface effect energy
MD simulation (thermal, strain, substrate)
7. Ref:
- Strain and support effects on phase transition and surface reactivity of ultrathin ZnO films: DFT insights
- Theoretical prediction of a phase transition in gold, PRB
- Layer-by-layer phase transformation in Ti3O5 revealed by machine-learning molecular dynamics simulations, NC
- Co HCP ==>> FCC, transition mechanism.
8. Thinking
思考影响因素
- 应变的影响（需要考虑不同厚度下应变的影响吗）
- 厚度的影响（对能量差的影响）
- 面内弹性常数/晶格常数的影响（晶格常数的降低导致了面内弹性常数的上升，晶格常数低会导致产生更小的压缩应变，同时弹性常数高更容易抵抗形变，且应变能在其中的影响也不可忽视）
- 表面能的影响（厚度、应变对表面能的影响，占比的影响，HCP可能表面能更低，但是得对应同一晶格常数）
- 化学刻蚀的影响（表面结构不稳定）
- 上下表面的压力的影响（下表面外延压缩应变、上表面是表面态原子，配位数缺失，导致给体相原子一个压应力，可以通过平衡原子晶格常数计算出来吗）
- 势垒的影响（层错能？厚度/应变对层错能的影响？块体中层错能和薄膜中层错能的比较，以及薄膜中不同上下区域的层错能）
- 相变驱动力（层错，可以计算不同厚度薄膜层错依次开动的能量/Atom的变化，直至块体）
复现了PRB文章中关于高压下HCP更稳定的情况
- Bain phase path - 针对FCC(001)-BCC(001)的相变，对金还没做过
- 外延Bain phase path - 可以对FCC(111)和HCP(0001)做分析，但是我觉得他两的 c/a 都没什么区别
- 实验上观察到的HCP薄膜是压应变（2.8/2.96/2.927 —> 2.54 埃 ）
II. High modulus and high strength design shceme for FCC/HCP phase
III. Irreversible phase change from graphene to diamane
0. Thinking
- Saturate the dangling bond
- plasma
- solute (H2O2, NaCl, KCl)
- high pressure
- AFM
- DAC
- high temperature
- AFM only ~200 ℃, maybe it’s not enough
1. Question
- 老板那篇Natrue Nano中的 SiC 基底是晶体/非晶？
- 晶体
2. Difficulty
Plasma + Indentation
- 氢气可行吗，配套的设施
- 压痕小装置：转移台的操作装置，加一个样品台，阵列探针，电机（可选，或者手拧螺丝）
Cypher AFM
- 水蒸气通（否决，没压力）
- 如何避免/区别氧化石墨烯？
IV. DFT - different substrate for gold / different saturated atoms
V. DFT - 面内应变对 gamma line 的影响
0. Theory
- Stress-dependence of generalized stacking fault energies.
VI. DFT+MD. 位错形核，位错运动 - HCP Au.
0. Theory
Strain direction dependency of deformation mechanisms in an HCP-Ti crystalline by molecular dynamics simulations
尹老师那篇
- The role of mechanical loading in bcc-hcp phase transition: tension-compression asymmetry and twin formation
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