[DFTB-Plus-User] Charge in dftb+ calculations

[Mat Toliday]

 Hello Anshu,DFTB, like other electronic structure methods, tries to determine the behavior of the electrons in the molecule you provide. Once the approximate electron wavefunctions are determined, then the effective charges on the atoms are calculated. This is the reason you can only provide initial charges, which is useful when trying to get DFTB to converge on a certain wavefunction (like a ferromagnetic or antiferromagnetic state). Otherwise DFTB will always try to converge on a physically reasonable ground state which will generally not be what a user provides in terms of initial charges. Perhaps you can explain why you were hoping to do this, it might others  help answer you question more fully.Mat
    On Thursday, 27 February 2020, 17:52:30 CET, Anshu Gaur via DFTB-Plus-User <dftb-plus-user at mailman.zfn.uni-bremen.de> wrote:  
 
 Dear all,

I am trying to add charge to a molecule (different amount of charge on 
different atoms of same type), which can be done by using 
"InitialCharges" option in the Hamiltonian. However, this only 
applicable if I do SCC calculation. SCC routine re-distributes charges 
equally among all atoms if the Charge (total charge in the system) is 
provided.

Is there a way to include Initia -charges and do non-SCC calculations so 
that charges added on different atoms remain as defined during 
calculations (such as force on atoms or other properties)?

Can MaxSCCIterations be set to '0' to avoid re-distribution of charges, 
or SCCTolerance be set to an arbitrarily high value so that SCC 
converges without any re-distribution of charges?

Regards,

Anshu


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