[DFTB-Plus-User] Spin polarization and other

[Mat Toliday]

 Hello,I don't think you can use DFTB+ inside of Gaussian but it claims to be capable of DFTB calculations. I spent a  couple of hours trying to modify the Slater-Koster files and then lost interest...I don't think DFTB+ has the geometry optimisers needed for TS searching but these can be found using another package alongside DFTB+, namely the Atomic simulation Environment which has lots of useful geometry/optimiser tools and will interface with DFTB+.As for your TS simulations:
I notice between your two input files there is a change in the total charge. This is most likely the the reason the dE value is too high.Yours,Mat

    On Tuesday, 3 December 2019, 14:49:47 CET, Martin Richter <m-richter93 at gmx.de> wrote:  
 
 Hello dear DFTB+ community, I have a few general questions and one specific problem. Id be very thankflul if you could help me.  - I assume you cannot use DFTB+ via gaussian? I have seen options for DFTB and DFTBA though. - I saw a question on 'spin polarization calculation' in the achrive, but no answer. Does this simply mean no one responded yet or did I miss something?- Are there anywhere some more examples? I went through the tutorials of the homepage, but cannot find more useful examples. - Can you perform transition state optimization ? And now my question regarding spin polarization. Im fairly new to QM chemistry so pardon any harsh mistakes. I want to study a hydrogen atom transfer reaction. To begin I just looked at CH4 + CH3* --> CH3* +CH4 (star * means radical). For the energy difference between precomplex and transition state (TS) I get from gaussian calculation  dE = 58 kJ/mol and literature tells me  dE = 39 kJ/mol. With my attempt in DFTB+ I get dE = 506 kJ/mol, which is way too much. Im wondering if I just made some mistakes or if maybe DFTB+ is not suited for this. Best regards and thanks,Martin My input files look like this: For TS: Geometry = GenFormat {
9 C
  C H
    1    1     -1.3492310000      0.0000000000     -0.0000040000                 
    2    2     -1.6387210000     -1.0390570000     -0.2023440000                 
    3    2     -1.6388130000      0.3443150000      1.0009990000                 
    4    2     -1.6386560000      0.6947620000     -0.7986980000                 
    5    1      1.3492320000      0.0000020000      0.0000070000                 
    6    2      1.6387010000     -0.6957490000      0.7978260000                 
    7    2      1.6387040000     -0.3431010000     -1.0014410000                 
    8    2      1.6387850000      1.0388000000      0.2035920000                 
    9    2     -0.0000060000      0.0000200000      0.0000490000                                
}Driver = {}Hamiltonian = DFTB {
  Scc = Yes
  SlaterKosterFiles {
    H-H = "/home/richtemn/Documents/DFTB+/recipes/slakos/mio-ext/H-H.skf"
    C-H = "/home/richtemn/Documents/DFTB+/recipes/slakos/mio-ext/C-H.skf"
    H-C = "/home/richtemn/Documents/DFTB+/recipes/slakos/mio-ext/H-C.skf"
    C-C = "/home/richtemn/Documents/DFTB+/recipes/slakos/mio-ext/C-C.skf"
  }
  MaxAngularMomentum {
    C = "p"    
    H = "s"
  }
  Charge = -1.0000000000000000
SpinPolarisation = Colinear {
UnpairedElectrons = 1.0
}
SpinConstants = {
C={-0.023}
H={-0.072}
}
 
}Options {}Analysis {
  CalculateForces = Yes
}ParserOptions {
  ParserVersion = 7
}  and for the precomplex: Geometry = GenFormat {
9 C
  C H
 1           1            -4.673     1.29559  -0.1981 
 2           2            -4.68347   1.67679   0.82361 
 3           2            -4.47712   1.97238  -1.03062 
 4           2            -4.8825    0.24263  -0.38913 
 5           1            -0.56698   0.5267    0.17636 
 6           2            -0.15029   0.1488   -0.76893 
 7           2            -0.42145  -0.22437   0.96669 
 8           2            -1.64234   0.72488   0.05129 
 9           2            -0.05174   1.45716   0.45691                                          
}Driver = {}Hamiltonian = DFTB {
  Scc = Yes
  SlaterKosterFiles {
    H-H = "/home/richtemn/Documents/DFTB+/recipes/slakos/mio-ext/H-H.skf"
    C-H = "/home/richtemn/Documents/DFTB+/recipes/slakos/mio-ext/C-H.skf"
    H-C = "/home/richtemn/Documents/DFTB+/recipes/slakos/mio-ext/H-C.skf"
    C-C = "/home/richtemn/Documents/DFTB+/recipes/slakos/mio-ext/C-C.skf"
  }
  MaxAngularMomentum {
    C = "p"    
    H = "s"
  }
  Charge = 0.0000000000000000
 SpinPolarisation = Colinear {
  UnpairedElectrons = 1.0
 } SpinConstants = {
  C={-0.023}
  H={-0.072}
 }}Options {}Analysis {
  CalculateForces = Yes
}ParserOptions {
  ParserVersion = 7
}_______________________________________________
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