I have calculated the partial charges using charge equilibration (Qeq) method. However, I would like to verified it using another methods such as extended charge (EQeq) or Density-Functional Theory (DFT).
I have read "An Extended Charge Equilibration Method" paper for Christopher E. Wilmer, Ki Chul Kim, and Randall Q. Snurr . However, I still need help with (EQeq) & (DFT) methods.
Thank you in advance
Hi.. I am here interested to know how to determine the partial charges from Qeq. Is there any automatic algorithm..
Hi to calculate charges by using Density-Functional Theory (DFT) method you can use gaussian.its a powerful software which is abale to calculate charges in two ways1-NBO 2-Mulliken.Nbo is better and more reliable
For DFT, basically getting the charge is to find a scheme to partition the charge density. I have a paper attached described a little bit about this problem. For practical, for molecules and finite systems, quantum chemistry codes like gaussian could do it (NBO is a good choice as Iman metioned). For periodic system, I use this code a lot (http://theory.cm.utexas.edu/henkelman/code/bader/), which is bader analysis. (VASP or QUANTUM ESPRESSO could be used to generate a charge density cube file).
For the Eqeq method, I think it is better to contact the author of the paper you provided.
Article Hirshfeld-E Partitioning: AIM Charges with an Improved Trade...
Being the first author of the paper mentioned above, I should probably comment as well. Your question is very very broad, so it is hard to give a complete answer.
There are many ways to compute QEq charges, i.e. there are many variants of this model going back to the 1980's (EEM, QEq, ABEEM, FlucQ, AACT, SQE, ACKS2, ...) and for most of these variants there are several parameterizations, such as EQeq for MOFs. Although some codes (like CP2K or ReaxFF) support one or more of these variants, you are better of contacting the author, just to be sure that you use the same flavor. It is usually not hard to code it yourself if you have same basic programming skills. A proper implementation of the Ewald sum is usually the hardest part.
DFT charges as such don't exist. One derives atomic charges from DFT electron densities or Kohn-Sham-DFT wavefunctions. Again, there are many different methods (I guess at least 100) and every quantum-chemistry program supports at least a few. Most implementations work only for isolated molecules. For periodic systems, the options are much more limited, e.g. the program of Henkelman mentioned earlier. Also HIVE (http://users.ugent.be/~devpouck/hive.shtml) and DDEC (http://sourceforge.net/projects/ddec/) could be an option. I have currently implemented another one that works very well for MOFs but it is not available yet. (Bear with me...)
We have published a paper comparing several charge methods using penta-alanine as a test molecule. That may be of interest: http://pubs.acs.org/doi/abs/10.1021/ct200512e
Hi Karteek K. Bejagam,
I used Materials Studio to calculate charges. The paper attached described a little bit about your question.
Hi Iman Rajaei,
Unfortunately, I don't have Gaussian software and I think it's not available in all the countries. Thanks
Thanks Yi Yao for your answer. I will try to use Bader Charge Analysis for my first time. I will email you if there is any results. Thanks again.
Thanks Toon Verstraelen for your answer and explanation. I am trying now to use Bader Charge Analysis and DDEC Atomic Charges, I hope it works. Thanks again.
I suugest to have a look at this paper: Atomic charges for modeling metal–organic frameworks: Why and how (http://dx.doi.org/10.1016/j.jssc.2014.08.004)
Besides reviewing several of most common methods, special attention has been put on basic questions, such as for a given force field what type of method should be used for calculating the charges, and also on the relevance of the correct description of the struture on the charge calculation
In regard to the last paper mentioned here, you could also have a look at Hirshfeld-I charges. These do not suffer from the problem of varying significantly when you change the topology.
J. Comput. Chem. 34(5), 405-417 (2013),
doi:10.1002/jcc.23088
see for example the SI of this paper:
J. Phys. Chem. C 119(41), 23752-23766 (2015),
doi: 10.1021/acs.jpcc.5b06809
Dear Dr. Al-Jadir,
You might have a look on this paper:
https://doi.org/10.1016/j.jssc.2014.08.004
https://www.researchgate.net/publication/268207356_Atomic_charges_for_modeling_metal-organic_frameworks_Why_and_how?_iepl%5BviewId%5D=4CmiVvFVFVRl1yg1OmHYZCFJ&_iepl%5BprofilePublicationItemVariant%5D=default&_iepl%5Bcontexts%5D%5B0%5D=prfpi&_iepl%5BtargetEntityId%5D=PB%3A268207356&_iepl%5BinteractionType%5D=publicationTitle
Best regards,
A. Rabdel Ruiz-Salvador
Article Atomic charges for modeling metal–organic frameworks: Why and how
Dear Dr. Al-Jadir,
Could you please explain how you obtained your charges using Qeq?
I am using Open Babel, but the partial charges I get are wrong because my simulations crash. Qeq using open babel gives me a positive charge surface that results in crashing. I also obtained partial charges from EQeq using Atomic Charge Calculator II which gave me a negative charge surface. Interestingly, I could do my simulations with that partial charge method, EQeq.
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