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[资源] 用VASP固定应力计算的python脚本（20171016更新增加了对切应力的支持）

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原帖：
脚本目的：用VASP实现指定应力张量下材料的DFT模拟，目前只支持主应变，尚未考虑切向应力
由于VASP程序本身不支持固定应力计算，本脚本通过广义胡克定律反推获得指定应力所需的应变，相应的调整POSCAR，不断重复迭代该过程直至获得所需应力状态。
附件是对bcc钨的单轴拉伸算例，脚本头部注释行有使用说明。
若发现任何bug，请致信jie.hou2@mail.mcgill.ca
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20171016更新：
最近有算切应力的需求，还是完善了对切应力的支持。附件1.0中是bcc钨的一个算例，随便设了一个应力张量：
-100 10 -50
10 100 100
-50 100 50
测试正常收敛，

另附简单说明
Instructions:
1. Input the pressure (stress) tensor in the script
2. Input estimated elastic modulus in the script
3. Set ISIF=2 in the INCAR
4. Copy POSCAR to poscar.0
5. Configure mpiexec commands in the script based on your linux environment
6. Use 'qsub $YourJobPath/fixpressure.py' to submit your job

Notes:
This script calculates stress tensor by using vasp program, and adjusts the POSCAR iteratively until the stress tensor converges to the value you want.
The POSCAR adjustment is estimated according to generalized Hooke's law based on elastic modulus you inputted. The iteration algorithm can tolerate certain errors in the modulus, but bad modulus input may lead to a slow convergence.
In order to obtain an accurate stress result, please use a high ECUT. See Vasp manual for details.
You can set ISTART=1 and LWAVE=.T. in the INCAR file, this can accelerate the calculation. However, this may also raise convergence problems when shear stresses are applied. Do your own tests.
Shoule you find any bug, please contact jie.hou2@mail.mcgill.ca.[ Last edited by 浔荆 on 2017-10-17 at 08:51 ]

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