How can we calculate the bond between two atoms is either covalent or ionic in nature in the frame work of DFT? (particularly by using vasp)
Hi,
ELF should give you straight forward answer and you can also visualise the nature of bonding. You can plot ELFCAR(CHGCAR format, use vesta or xcrysden) with VASP. You need to perform a static calculation from pre-converge WAVECAR (LELF = .TRUE., ISTART=1). Once you have ELFCAR, plot isosurface and change the iso-value from 0.0 to 1.0. If you find that with large ELF(~1-0.65) value, the iso-surfaces remain localized on individual atoms. on the other hand, If the iso-surfaces lies on the bond, between the atoms (say close to mid-point of the bond, for a bond between similar atoms), it indicates covalent bonding. Please follow the link in my last post for further details.
The terms Covalent and ionic sometimes are miss leading for describing a bond. to answer your question i will suggest doing some NBO calculation, from that you will be able to determine the %S %P and %d character of atoms involve in a bond formation. That way you ca determine the covalency of the bond
Electron Localization function (ELF) is often used to quantify the ionic vs. Covalent bonding. In ionic systems, with large ELF value, the iso-surfaces remain localized on individual atoms. See the link for more details.
http://www.lct.jussieu.fr/pagesperso/savin/papers/ed-sason/revision1.pdf
You can calculated the electronic density and use the theory of Atoms In Molecules (AIM) described by Bader.
Hirshfied charge analysis, Vironoi Charge Analysis and mullikan populations charge analysis techniques are used for electronic density to study ionic or covalent characters.
Electronegativity is also a major property for the above said problem
Thank you for your suggestions. In fact, I am interested to know key parameters and values of charge transfer between two atoms which predict/define the bonding between two atoms in a molecule or in honeycomb structure. Here, my question is not limited to only charge transfer analysis methods, but also want to know how to define the bonding nature between two atoms?
Hi,
ELF should give you straight forward answer and you can also visualise the nature of bonding. You can plot ELFCAR(CHGCAR format, use vesta or xcrysden) with VASP. You need to perform a static calculation from pre-converge WAVECAR (LELF = .TRUE., ISTART=1). Once you have ELFCAR, plot isosurface and change the iso-value from 0.0 to 1.0. If you find that with large ELF(~1-0.65) value, the iso-surfaces remain localized on individual atoms. on the other hand, If the iso-surfaces lies on the bond, between the atoms (say close to mid-point of the bond, for a bond between similar atoms), it indicates covalent bonding. Please follow the link in my last post for further details.
Hi, you can follow Prof. Dr. P. Pyykkö research "http://www.chem.helsinki.fi/~pyykko/"
Hi,
if you have calculated DOS of system you can see the behavior of two kind of atoms involved in the bond. In particular, one can analyzes the mechanism of hybridization, in principle, driven by the formation of a covalent bonding, caused by the sharing of an electronic cloud between them. From DOS it's possible to show this fact analyzing the peaks corresponding to specific orbitals interacting (the outer orbitals). If there is a almost-perfect overlap between them, one may say that some hybridization acts. Otherwise, with high probability, the two don't interact so strong to bond covalently. This fact doesn't guarantee that the bonding is ionic, but one can verify this through the analysis of charge density and band structure. With the first analysis it's possible to evaluate if there is a localization of charge (ionic) or a locally distributed charge (covalent). The second is a confirmation of a possible transfer of charge from one to another element. In that case there is a N-doping of the matrix structure, doped with excess electron by the donor.
Best,
A.
What is the role of atomic radii and bond lengths in the formation of covalent bonds between the atoms?
Here is the best way to quantify the amount of covalent versus ionic bonding in a material:
(1) Compute the net atomic charges and the bond orders using method described in these papers: http://dx.doi.org/10.1039/c6ra04656h, http://dx.doi.org/10.1039/c6ra05507a, http://dx.doi.org/10.1039/c7ra07400j (last one is open access). This method is implemented in free Chargemol program (http://ddec.sourceforge.net)
(2) If the material has primarily ionic bonding, the net atomic charges will be large in magnitude and the bond orders will be small. If the bonding is polar-covalent, the net atomic charges will be significant (>= 0.3 in magnitude) and the bond orders will also be substantial. If the bonding is covalent, the net atomic charges will be small while the bond orders will be significant.
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