ONIOM计算后如何在fchk文件中保存轨道信息

pwzhou

最近用ONIOM做点TD计算，计算完以后想看下轨道，结果发现fchk文件中居然没有轨道信息，搜索了一下没找到答案，于是给Gaussian公司写了封邮件，询问了一下，得到了如下答复，共享给大家。我已经试过，顺利得到了所需的High Layer的轨道信息。

Each ONIOM subcalculation may have a different set of MOs. You may use the "formchk" utility to generate separate formatted checkpoint files (fchk), one for each subcalculation so one can examine the different sets of MOs independently. The formchk flag that you need to use with ONIOM is the following:

"-XY" with
"X" being L, M, H for "Low", "Medium", "High" levels and
"Y" being L, M, S for "Large", "Medium", "Small" size systems

Here is an example of the 6 possible different formatted checkpoint files that you can generate for your 3-layer ONIOM job:

a) High level (td=(nstates=12)/b3lyp/tzvp) calculation on Model system (High layer atoms plus link atoms):

formchk -HS FIMe-cluster-abs2-2.chk FIMe-cluster-abs2-2_HighModel.fchk


b) Medium level (am1) calculation on Model system (High layer atoms plus link atoms):

formchk -MS FIMe-cluster-abs2-2.chk FIMe-cluster-abs2-2_MedModel.fchk


c) Low level (uff) calculation on Model system (High layer atoms plus link atoms) [obviously no MOs in this one]:

formchk -LS FIMe-cluster-abs2-2.chk FIMe-cluster-abs2-2_LowModel.fchk


d) Medium level (am1) calculation on Intermediate system (High and Middle layer atoms plus link atoms):

formchk -MM FIMe-cluster-abs2-2.chk FIMe-cluster-abs2-2_MedInt.fchk


e) Low level (uff) calculation on Intermediate system (High and Middle layer atoms plus link atoms) [obviously no MOs in this one]:

formchk -LM FIMe-cluster-abs2-2.chk FIMe-cluster-abs2-2_LowInt.fchk


f) Low level (uff) calculation on Real system (all atoms) [obviously no MOs in this one]:

formchk -LL FIMe-cluster-abs2-2.chk FIMe-cluster-abs2-2_LowReal.fchk


After you have the formatted checkpoint file (fchk) with the desired set of MOs from the ONIOM job, just open the formatted checkpoint file in GaussView for visualization. According to your email, if you only want to look at the MOs that were used in the TD subcalculation, you only need to generate the FCHK file from a) above (High Level calculation on Model system)


By the way, for a 2-layer ONIOM job, you only have 3 different subcalculations:

a) High Level calculation on Model system (-MS)

b) Low Level calculation on Model system (-LS)

c) Low Level calculation on Real system (-LM)