UT theoretical chemistry code forum

Dear Graeme,

Does NEB method work for the TS searching in bond rotation? For example, I want to calcuculate the energy barrier of C-C bond rotation in ethonal, however, the results of neb calculation is quite strange. After several hundreds steps, I cannot find obvious high energy point, the energy ...

Dear Graeme,

Thank you for your prompt reply.
I still have queries for Q3:
I'm searching TS with initial guess from NEB calculation. When the forces in the neb caluculation are low enough (as below), I use the image 5 as intial guess and carried out dimer calculation.
0 0.04431500 1398.46409800 0 ...

Dear Graeme,

I'm using Dimer method to search TS, starting from an NEB calculation.
1. Although the force is converged and the curvature is negative, the angle remains high. I'm not sure what the problem is. Here is the DIMCAR file:
Step Force Torque Energy Curvature Angle
1 0.45114 11.19323 ...

Thank you very much !
I'm using CI-NEB method, so I don't need run a dimmer calculation to confirm saddle point, right? I read your previous post, you mentioned " The climbing image takes away the need to increase the density of images near the saddle -- there only needs to be enough points in the ...

Dear Sir,

Thank you for your reply.
Another question, can I calculate the two pathways ( 1. from start state to intermediate structure, 2. from intermediate structure to final state) respectively, then combine the two pathway together to get MEP?

Thanks again

Zhang Jia

Dear Sir,

Thank you for your reply.

I tried to interpolate three images between start and final state. It seems that the energy and force are reasonable.
First, I run the job with POTIM = 0.01 for 300 ionic iterations
The "nebef.pl" script give
0 0.03601800 -121.36430300 0.00000000
1 0.04227000 ...

Dear Sir,

I run my job with POTIM=0.01 unitil the forces drop to about 0.5eV/Ang, then increase POTIM =0.1; also I run the job with POTIM= 0.01 all the time. However, after 5000 steps both jobs have not converge yet. I find it is awkward to visualize the OUTCAR and the structure goes crazy. The ...

Dear Sir,

In NEB method, if I get one image between initial state and end state, can I devide the MEP into two sections? I mean the first section is from initial state to image 1 (which is the new final state); and the second section is from image 1 (which is the new inital state) to final state ...

Sorry to bother you again.

Here is the new force information at 25th iteration when POTIM = 0.01 is performed. You mentioned the forces drop below 1eV/A. Does it point to "Force total" or "Forces: max atom, RMS"? There are several force values, I 'm not sure which one is the benchmark.

Many Thanks ...

Thanks, Graeme. I'll try.

Thank you for your prompt reply.

Here is the force information after the 1st iteration. It seems that the forces are quite big. I wonder which force I should check, is it "Forces:max atom, RMS ...."?

In addition, the current image is generated by nebmake.pl script.
I should use neb_pushapart.pl ...

Dear Sir,

I'm trying to calculate MEP using Climbing NEB ( 1 or 3 images are interpolated), however, it is not convergent. The energy is very strange, goes to a possitive value.
I find there's the warning information in the output file "WARNING in EDDRMM: call to ZHEGV failed, returncode = 6 3 3 ...