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VASP MD 得到 amorphous结构已有1人参与
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大家好。我想利用VASP跑分子动力学模拟得到amorphous结构。思路大概是从crystalline phase起先melt再quench。有一个问题是，amorphous phase的密度一般比crystalline phase密度要低，所以其晶格常数要大一些。如果始终用NVT ensemble的话晶格常数不会改变，这样得到的结构不太合理，因为得到的amorphous 结构密度和crystalline phase一样，会存在很大 residual stress。所以我试着用NpT ensemble (ISIF=3)，保持压强为一个大气压，期望晶格常数会有所增加，得到合理的结构。现在问题是，NpT MD时候晶格常数一直不变，请问怎么回事？ INCAR file： # General parameters for this run System= SnO2 NCORE = 12 # Electronic specification PREC = Normal ! standard precision, we recomend the use of PREC = Normal ENCUT = 150 ! cutoff should be set manually, smaller if ultra-large supercell ISMEAR= 0 SIGMA = 0.01 LREAL = Auto ! Real space to spped up for large molecular dynamics runs ALGO = Very Fast ! For large molecular dynamics runs NELMIN= 4 ! Set minimum steps of electronic optimization EDIFF = 1E-3 ! Do not use default, too much drift # MD related # NpT ISYM = 0 ! strongly recommened for MD, no symmertry IBRION= 0 ! molecular dynamics NSW = 7500 ! 7500 steps POTIM = 2 ! timestep 2 fs # SMASS = -1 ! Nose Hoover thermostat ISIF = 3 MDALGO= 3 ! TEBEG = 3000 TEEND = 300 ! temperature PSTRESS= 0.001 # Output control NBLOCK= 50 ! XDATCAR updated every 50 steps NWRITE = 0 ! For MD, use NWRITE = 0 or NWRITE = 1 LCHARG = .FALSE. LWAVE = .FALSE. |
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6楼2020-01-31 11:41:30
Nano2016
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2楼2020-01-30 12:00:03
valenhou001
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3楼2020-01-30 12:00:18
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4楼2020-01-30 12:36:02
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这个可以对模拟元胞进行缩放，计算不同体积对应的压力，拟合p-v曲线，得到你想要的压力对应的体积。我最近的文章计算方法里有这方面的内容，可以参考https://doi.org/10.1016/j.molliq.2019.112063 发自小木虫Android客户端 |
5楼2020-01-31 11:36:28
7楼2020-02-03 02:04:56
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我也是查的manual设置的。有些参数不知道怎么设置就leave it default. NpT要怎么设置？ 1. Set the standard MD-related tags: IBRION=0, TEBEG, POTIM, and NSW. 2. Set ISIF=3 to allow for relaxation of the cell volume and shape. At the moment, dynamics with fixed volume+variable shape (ISIF=4) or fixed shape+variable volume (ISIF=7) are not available. 3. Set MDALGO=3 to invoke the Langevin thermostat. 4. Specify friction coefficients for all species in the POSCAR file, by means of the LANGEVIN_GAMMA-tag. 5. Specify a separate set of friction coefficient for the lattice degrees-of-freedom, using the LANGEVIN_GAMMA_L-tag. 6. Set a mass for the lattice degrees-of-freedom, using the PMASS-tag. 7. Optionally, one may define an external pressure (in kB), by means of the PSTRESS-tag. |
8楼2020-02-03 02:08:20
9楼2020-02-03 02:09:37
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我也是查的manual设置的。有些参数不知道怎么设置就leave it default. NpT要怎么设置？ 1. Set the standard MD-related tags: IBRION=0, TEBEG, POTIM, and NSW. 2. Set ISIF=3 to allow for relaxation of the cell volume and shape. At the moment, dynamics with fixed volume+variable shape (ISIF=4) or fixed shape+variable volume (ISIF=7) are not available. 3. Set MDALGO=3 to invoke the Langevin thermostat. 4. Specify friction coefficients for all species in the POSCAR file, by means of the LANGEVIN_GAMMA-tag. 5. Specify a separate set of friction coefficient for the lattice degrees-of-freedom, using the LANGEVIN_GAMMA_L-tag. 6. Set a mass for the lattice degrees-of-freedom, using the PMASS-tag. 7. Optionally, one may define an external pressure (in kB), by means of the PSTRESS-tag |
10楼2020-02-03 02:10:49
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