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[求助]
vasp优化结构报错ZBRENT: fatal error in bracketing 已有1人参与
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各位大神，刚刚使用vasp不久，优化结构总是遇到一些问题，根据网上查询的办法似乎都没有什么效果，所以请有懂的大神能够给予一点指导，感激不尽。 ZBRENT: fatal error in bracketing please rerun with smaller EDIFF, or copy CONTCAR to POSCAR and continue 我是采用ISIF=2,ISIF=7,ISIF=2,ISIF=7的方式，来优化结构的，对于unit cell来说，优化的很好。然后超胞后，改变锂离子的数目，优化一些结构。再优化这些结构时，先采用ISIF=2优化成功，然后ISIF=7优化晶格常数，但这一步一直无法成功，总是出现上面的错误。 试过的方法： 1. 根据提示CONTCAR变POSCAR继续优化，或者使用更小的EDIFF，都仍然一样的报错。 2. IBRION改为1计算，现在已经算了120个离子步了还未收敛，优化结构后面实时更新。 3. IBRION=1，并且ADDGRID=TRUE进行优化，优化结构后面更新。（ADDGRID简单测试了一下，似乎对能量没有什么影响） 4. IBRION不变，仍然=2，加入ADDGRID=TRUE进行优化，结果后面更新。 现在通过查资料找到的就这些方法。 请问大家： 1. 这个报错的原因是什么？ 2. 如何有效解决这个报错呢？ 3. 看到有人说这个跟vasp的编译有关？请问这个该如何理解，具体指什么相关呢？ （本人不太相信这种原因） 4. ADDGRID的具体含义是什么，有什么影响？vasp计算好像很少看到这个参数。 本人的输入文件均已上传。 请大家能够花点时间一起讨论一下，Thanks a lot ! |
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【答案】应助回帖
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感谢参与，应助指数 +1
李玥玥: 金币+15, ★★★很有帮助 2017-07-17 19:45:03
漫天飘雪: 金币+2, 谢谢交流 2017-07-17 20:45:33
感谢参与，应助指数 +1
李玥玥: 金币+15, ★★★很有帮助 2017-07-17 19:45:03
漫天飘雪: 金币+2, 谢谢交流 2017-07-17 20:45:33
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?@???}????????F ?????o????l??????????VASP??????????????????^??? http://cms.mpi.univie.ac.at/vasp ... ?f=3&t=7415 ?e??? admin (????? VASP ???????????T???????m???_??????~ ????? VASP ???????????P?B) please have a look at the OUTCAR file, at the forces of the last ionic step before Brent's algorithm fails -- if the calculation is very well-converged already, please proceed using IBRION=1; ADDGRID=.TRUE. and a larger ENCUT ?@??c???c???????????? 3 ?????? ???^??????????????????? "???" ????? -- if this error appears at an early stage of the relaxation, pelase check if your input geometry was reasonable, eg by having a look at the interatomic distances (written in OUTCAR) or the forces of the first geometries. It may then help to increase the accuracy (PREC= Accurate and a higher ENCUT) and to decrease POTIM to avoid too large stepwidhts in the first relaxation step. ???????????x???????h????z?????Y???????? ?z?? OUTCAR ?????? ionic loop ?? FORCE????????????????F????????????? ??^ PREC=Accurate & ENCUT ??? & ???? POTCAR????S??????? http://cms.mpi.univie.ac.at/vasp ... p?f=3&t=869 this message says that during geometry optimisation no reasonable next step could be found with Brent's algorithm (linear bisectioning) please check the following 1) is the system converged already? (look at the forces in OUTCAR, especially if you use the total energy change as congvergence criterium for ionic optimisation) 2) if not: is each ionic step converged electronically ( this is needed to obtain reasonable forces) ?@??????????????С????????admin ?????????????f sometimes, if the calculation is already highly converged, vasp cannot interpolate the next step to within the numerical accuracy because it simply would be so small. (this behaviour is machine-dependent). If you have used IBRION=2, it may help to switch to IBRION=1 and set ADDGRID=.true. in addition ???c???c???f???Q???? 4 ????? ???? http://cms.mpi.univie.ac.at/vasp-forum/viewtopic.php?t=1856 ZBRENT is an algorithm search for a root of a function by Brent's method: Numerical recipies, Section 9.3 The problem in your case might be that the Conjugate Gradient algorithm (IBRION=2) is not suitable for very small corrections of the atomic positions if your system has almost reached equilibrium (please have a look at XDATCAR to check the size of the relaxation steps done before the ZBRENT warnings show up). Usually it is sufficient to converge a system up to maximum remaining forces of about 0.01eV/A (EDIFFG=-0.01). please try one of the following: 1) choose a different algorithm for ionic optimization (IBRION=1) 2) set ADDGRID=.True. in INCAR (only for vasp releases 4.4.5 and newer) Admin ?? ZBRENT ???????f?? ZBRENT ?ǔ????????? Brent's method ??????????????????r??VASP ?????? displacement ??????С ???п????????@?? Brent's method ?a?????} ?????? ?@???}?????F?? structure optimization ?r ???????VASP???? optimized position ?a??????U ??????? (???????????????????S??o??) ?????????λ?????? 0.5 ???F??λ???? 0.4?????VASP????? 0.2 ??????? 0.4 ???? 0.6 ????????? 0.4 ???????? 0.6 ??????????o???????? ?Y???c?????????????????g????U ?@??????N??? IBRION ???ЙC???????Q?@???} |
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金币不多，大家见谅，附上INCAR和KPOINTS，上传出问题了。。。。 INCAR: SYSTEM = LiFePO4_1 ######Start Parameter for This Run ISTART = 0 ICHARG = 2 INIWAV = 1 ######Electronic Relaxation ENCUT = 520 NELM = 60 EDIFF = 1E-5 GGA = PE ISMEAR = 0 SIGMA = 0.05 PREC = Accurate ISPIN = 2 #LORBIT = 10 ######Ion Relaxation IBRION = 2 ISIF = 2 NSW = 200 EDIFFG = -0.01 POTIM = 0.5 ALGO = Fast LREAL = A NPAR=4 ######LDA+U LMAXMIX = 4 LDAU = .TRUE. LDAUTYPE = 2 LDAUL = 2 -1 -1 -1 LDAUU = 5.3 0 0 0 LDAUJ = 1.0 0 0 0 #for out LCHARG = .FALSE. LWAVE = .FALSE. LVTOT = .FALSE. LELF = .FALSE. KPOINTS: k-points 0 Monkhorst Pack 4 3 4 0 0 0 欢迎大家发言 |
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