UT theoretical chemistry code forum

thanks a lot, Graeme....I will do a further look and update here if i find something interesting

i didnt try the dynamical matrix calculation; but i tried to use ibrion=5 as a quick test;

the extremely small negative frequencies are generally representing lateral displacment, or translation which are not real; only the one roughly along rxn coordinates, strech of an old bond is real

Thx a lot, Graeme; here is the calculation; i removed the CHARGE file since its way too big; The geometry of this saddle point should be alright and the climbing NEB managed to converge it down to a force of 0.02 ev/A lately; There is something missing in my mind regarding the parameters in the dime...

Hello, all I am starting to learn dimer method as a means to achieve a more accurate saddle point; my first trial was running, though showing an unhealthy DIMCAR as: Step Force Torque Energy Curvature Angle 1 0.07200 9.95315 -761.18452 -0.20945 24.31446 1 0.07200 12.68468 -761.18452 1.34022 19.30569...

thx, Graeme

I am moving on to analyze the vibration after a set of sucessful c-NEB calculation. To my perhaps limited understanding, such a vibration analysis could give me information as: 1) confirm the transition state by giving only one imaginary frequency 2) give pre-factor in arrhenius formula (from imagin...

Quite often i am running into a problem with one or two images fluctuating between two clearly resolved states, making the whole NEB calculation not converged to a satisfying extent. I read through the old posts regarding this but still have some questions, calling for professional help. Generally s...

i guess i figured it out; this is due to the process i am calculating involves two barriers with similar heights; the strategy is to break them apart. also the maxmove in the default is a bit too large for me; i need to lower it down to 0.02 (default 0.2)

indeed, now i managed to converge everything down to 0.02 eV/A by breaking them into two parts for two individual climbing NEB;

Thanks

thx, graeme could you tell me a bit more how it determines to push which image to saddle point in the current versioned neb? is it as simple as pushing the highest energy image at certain iteration? it would be lovely to have such a tag to find all the extremes; but based on my reading of the old po...

i had suffered similar problem before and it turned out to be related to my pathway involving two barriers with similar heights. if that is what you have, probably its better to break down the calculation

I am now facing a problem that I am suspecting to be related with the "climbing" part of the NEB calculation. My current cacluation seems to show two barriers between my initial and final states. Anoyingly, these two barriers seem to be quite close in energy (~0.1 eV), making it difficulty...

thanks, Graeme; I am testing it and would post the result. This is regarding the molecular dissociation on silicon surface. The whole reaction appears to involve of two separate saddle points en route from initial to final states (two bumps in 1D energy profile). Quite interestingly, these two saddl...

Could anyone tell me a bit more regarding the tag "LDNEB", implemented as a double nudging (variable spring constant)? how vasp would change spring constant if i use this tag to apply to the connection between different images? I am facing a peculiar difficulty to further converge a set of...

thx, Graeme