vasp中解决SCF不收敛的方法之一

zhongyuabc

最近在使用ALGO=Fast时，第二离子步中的SCF不收敛。手册中提到NELM gives the maximum number of electronic SC (selfconsistency) steps which may be performed. Normally, there is no
need to change the default value: if the self-consistency loop does not converge within 40 steps, it will probably not converge at all. In this case you should reconsider the tags IALGO, (ALGO ), LDIAG , and the mixing-parameters.所以重新阅读手册中的ALGO部分，又提到A faily robust mixture of both algorithm is selected for ALGO = Fast. In this case, Davidson (IALGO = 38) is used for the initial phase, and then VASP switches to RMM-DIIS (IALGO = 48). Subsequencly, for each ionic update, one IALGO = 38 sweep is performed for each ionic step (except the first one) 。也正是因为这句话，我才会一开始使用ALGO=Fast.
但是接下来又在手册中看到这样一段话：The most extensive tests has been done for IALGO = 38 (IALGO = 8 before VASP.4.5). If random vectors (INIWAV = 1) are used for the initialization of the orbitals, this algorithm always gives the correct KS groundstate. Therefore, if you have problems with IALGO = 48 (ALGO = Fast) switch to IALGO = 38.

果断把我的ALGO改为Normal，接着就不再有SCF不收敛的情况，而且优化速度比之前ALGO = Fast快很多。按手册说法，应该是ALGO=Fast算得更快。而我的使用ALGO=Normal之所以快，是因为每一步中SCF次数都很少。