Multiwfn forum

Hello.
I'm studying rotational barrier of ethane when it goes from staggered to eclipsed with a combination of techniques in which the QTAIM is one of the main ones. So, one of the main methods to do this type of study is to optimize the staggered conformer, then rotate the C-C bond to eclipsed conformer but do not optimize any other geometric parameter, so you are left with dihedral angle of eclipsed conformer but bond length and 3 atom angles of staggered conformer, something like a "staggered-eclipsed" conformation. Finally you optimize the eclipsed conformer. This leaves you with 3 conformers, the staggered being the lower in energy, the "staggered-eclipsed" being the higher in energy and the eclipsed being the middle term in energy. This is what i get from the single point calculation performed with MP2/ma-def2-QZVPP level of theory. When i use QTAIM to separate these 3 conformers into atomic basins, the summation of the electronic energy of all basins of a given conformer should give me the molecular electronic energy of that conformer just like the single point energy. So i sum up all the basins electronic energies and i have the molecular electronic energy just like the one from the single point except for the "staggered-eclipsed" conformation. This one is lower in energy than the other two conformers even though it should be the higher. Does anyone have any idea why QTAIM reproduces the molecular energy for the staggered and for the eclipsed conformers but not for the "staggered-eclipsed" conformer?

Thank you.
Att. Vinícius Martinelli

Hello fellows.
I read in manual that ESP analyzes the potentials on vdW surface, wich is the isosurface with 0.001 a.u. of electron density.  So if i'm analyzing my molecule through QTAIM, and i calculate properties like ESP and electrostaic potential from electrons or atomic charges, as those are functions of r i imagine that r is the distance between the nuclear attractor and the isosurface where the electron density is 0.001 a.u wich also would be the distance between the nuclear attractor and the bond critical point right?. As the isosurface is not a sphere, r would vary and so would ESP and the other potentials along with r, so the value i get is an average over the surface. Am i right?

Hello guys.
I'm a new worker with this tool and i'm loving it.
So my doubt might be dumb, but please help me.
When i go to basin analysis, electron density, hamiltonian kinetic energy density K(r), i get basin energies that when added all up give me a value very close to the single point energy calculation value obtained with ORCA or GAMESS wich is great.
When i go to topology analysis with electron density (analytical Hessian) as real space function chosen, and then output the properties for my molecule critical points, the energy values do not match the K(r) values from the basin analysis. Why is that? I imagined that the energy value for a certain atom basin should be the same regardless i use K(r) from basin analysis or topology analysis.
I also want to study the electron density change that a bond suffers when my molecule changes it's conformation. Can i use the density of all electrons from the CPprop.txt file gotten from topology analysis?
Thank you very much.