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tuhaidan

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[求助] 断电 ISTART=1 WAVECAR:different cutoff or change in lattice found

大家好,我在进行结构优化时候,断电了,我想接着算,于是ISTART=1,其他保持不变,显示WAVECAR:different cutoff or change in lattice found 这有问题吗?
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cavediger

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liliangfang(金币+1): 多谢指教,说的对 2012-02-09 08:43:42
没算完哪来的WAVECAR?
一般中间夭折想再继续的话,cp CONTCAR  POSCAR 其余不变......
我们都老得太快,却聪明得太迟。当我一路跌跌撞撞登上山巅,蓦然发现,本来就有一条笔直的路,直达山顶....
2楼2012-02-09 05:53:12
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gtssongchi

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uuv2010(金币+1): 多谢提示 2012-02-09 10:30:15
tuhaidan: 金币+1 2012-04-06 21:46:34
tuhaidan: 金币+2 2012-04-07 21:17:33
估计你的优化改变了cell的形状或体积,或者截断能改变了,如果是这样的话应该用ISTART=2,手册中有提到ISTART=1和2的区别。
3楼2012-02-09 09:54:23
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fanarsenal

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liliangfang(金币+1): 多谢提示 2012-02-10 12:45:12
tuhaidan: 金币+1 2012-04-06 21:46:22
看一下你的INCAR里面是不是少了东西,比如忘记了设置ENCUT使得其采用了默认值……
4楼2012-02-10 11:15:13
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静@思

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3楼: Originally posted by gtssongchi at 2012-02-09 09:54:23:
估计你的优化改变了cell的形状或体积,或者截断能改变了,如果是这样的话应该用ISTART=2,手册中有提到ISTART=1和2的区别。

ISTART=2和=1有什么区别?
5楼2012-04-03 21:45:37
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tider

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sunyang1988: 金币+1, 谢谢交流 2012-04-06 08:36:26
tuhaidan: 金币+1 2012-04-06 15:07:14
引用回帖:
5楼: Originally posted by 静@思 at 2012-04-03 21:45:37:
ISTART=2和=1有什么区别?

ISTART=1:
``restart with constant energy cut-off''. Continuation job -- read wave functions from file WAVECAR (usage is restricted in the parallel version, see section 4.5).
The set of plane waves will be redefined and re-padded according to the new cell size/shape (POSCAR) and the new plane wave cut-off (INCAR). These values might differ from the old values, which are stored in the file WAVECAR. If the file WAVECAR is missing or if file WAVECAR contains an inappropriate number of bands and / or k-points the flag ISTART will be set to 0 (see above). In this case VASP starts from scratch and initializes the wave functions according to the flag INIWAV.

The usage of ISTART=1 is recommended if the size/shape of the supercell (see section 7.6) or the cut-off energy changed with respect to the last run and if one wishes to redefine the set of plane waves according to a new setting.

ISTART=1 is the usual setting for convergence tests with respect to the cut-off energy and for all jobs where the volume/cell-shape varies (e.g. to calculate binding energy curves looping over a set of volumes).

Mind: main.f can be recompiled with new settings for NGX,NGY,NGZ,NPLWV ... between different runs, the program will correctly repad and reorganize the 'storage layout' for the wavefunction arrays etc. In addition it is also possible to change the k-point mesh if the number of k-points remains constant. This might be of importance if a loop over a set of k-points (band-structure calculations) is performed.


ISTART=2:
'restart with constant basis set': Continuation job -- read wave functions from the file WAVECAR
The set of plane waves will not be changed even if the cut-off energy or the cell size/shape given on files INCAR and POSCAR are different from the values stored on the file WAVECAR. If the file WAVECAR is missing or if the file WAVECAR contains an inappropriate number of bands and/or k-points the flag ISTART will be set to 0 (see above). In this case VASP starts from scratch and initializes the wave functions according to the flag INIWAV. If the cell shape has not changed then ISTART=1 and ISTART=2 lead to the same result.

ISTART=2 is usually used if one wishes to restart with the same basis set used in the previous run.

Mind: Due to Pullay stresses (section 7.6) there is a difference between evaluating the equilibrium volume with a constant basis set and a constant energy cut-off -- unless absolute convergence with respect to the basis set is achieved! If you are looking for the equilibrium volume, calculations with a constant energy cut-off are preferable to calculations with a constant basis set, therefore always restart with ISTART=1 except if you really know what you are looking for (see section 7.6).

There is only one exception to this general rule: All volume/cell shape relaxation algorithms implemented in VASP work with a constant basis set, so continuing such jobs requires to set ISTART=2 to get a 'consistent restart' with respect to the previous runs (see section 7.6)!
6楼2012-04-06 00:00:12
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静@思

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6楼: Originally posted by tider at 2012-04-06 00:00:12:
ISTART=1:
``restart with constant energy cut-off''. Continuation job -- read wave functions from file WAVECAR (usage is restricted in the parallel version, see section 4.5).
The set of plane w ...

但是我有一个问题是优化没有算完,文件中的WAVECAR和CHGCAR这两个文件是空的?这是怎么回事?这两个文件只有在优化结束后才会有啊,这样的情况怎么接着计算?(不知大家注意到了没有,wavecar和chgcar这两个文件只有在优化结束时才会写入,一开始只写入chg文件,所以我不知道大家接着计算的时候设置ISTART=1或者2有什么意义,这样设置的前提是有wavecar文件啊),谢谢
7楼2012-04-06 08:29:56
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tider

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sunyang1988: 金币+1, 谢谢交流 2012-04-06 12:01:32
tuhaidan: 金币+1 2012-04-06 15:07:28
引用回帖:
7楼: Originally posted by 静@思 at 2012-04-06 08:29:56:
但是我有一个问题是优化没有算完,文件中的WAVECAR和CHGCAR这两个文件是空的?这是怎么回事?这两个文件只有在优化结束后才会有啊,这样的情况怎么接着计算?(不知大家注意到了没有,wavecar和chgcar这两个文件只 ...

记得侯博那个指南上有说断电后只要设置ISTART=1和ICHARG=1即可。不过我没有用过,你可以试试,另外参考3楼意见。另外你是在做弛豫计算么?若如此你可以参考2楼意见,每一步弛豫的结果都写在CONTCAR里面的。WAVECAR里面虽然没有东西,但只要有这个文件,还是可以读取的。
8楼2012-04-06 08:59:19
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静@思

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8楼: Originally posted by tider at 2012-04-06 08:59:19:
记得侯博那个指南上有说断电后只要设置ISTART=1和ICHARG=1即可。不过我没有用过,你可以试试,另外参考3楼意见。另外你是在做弛豫计算么?若如此你可以参考2楼意见,每一步弛豫的结果都写在CONTCAR里面的。WAVEC ...

是的,我是在做弛豫计算,呵呵。我现在就是按照把contcar考成poscar然后重新计算,这样其实也是接着停电之前算了吧,我是这样认为的。
9楼2012-04-07 10:18:56
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