3ob-3-1

This set of parameters is part of the Third-Order Parametrization for Organic and Biological Systems (3OB) has been specifically designed for Third Order Density Functional Tight Binding (DFTB3) and supersedes the mio parameter set. Main improvements over mio are improved geometries for non-covalent bonds as e.g. the hydrogen bond in the water dimer, a great reduction of the consistent overbinding and an overall improved performance. Comprehensive benchmark tests for C-H-N-O can be found in [JCTC2013], for P-S-* in [JCTC2014], for Mg-Zn-* in [JCTC2015-1], and for Na-F-K-Ca-Cl-Br-I-* in [JCTC2015-2].

The following zeta and Hubbard derivative parameters should be used for DFTB3 calculations (atomic units). Use the DampXHExponent in DFTB+ in order to specify it.

zeta  4.00

List of all atomic Hubbard derivatives (atomic units). Use the HubbardDerivs option in DFTB+ in order to specify them.

Br-0.0573Mg-0.02
C-0.1492N-0.1535
Ca-0.0340Na-0.0454
Cl-0.0697O-0.1575
F-0.1623P-0.14
H-0.1857S-0.11
I-0.0433Zn-0.03
K-0.0339

List of maximum angular momenta. Use the MaxAngularMomentum option in DFTB+ to specify them.

BrdMgp
CpNp
CapNap
CldOp
FpPp
HsSd
IdZnd
Kp

For the empirical halogend bond correction described in [JCTC2015-2]
the following parameters are provided:

DFTB3-D3(BJ) Parameters:
a1 = 0.746
a2 = 4.191
s8 = 3.209

General X-Correction parameters (AA and kcal/mol unit system):
c1 = 7.761
c2 = 0.050
c3 = 4.518

Element Pair Parameters (AA and kcal/mol unit system):
O-Cl = 1.237
O-Br = 1.099
O-I  = 1.313
N-Cl = 1.526
N-Br = 1.349
N-I  = 1.521

Publications to be cited

O - N - C - H [JCTC2013]
P,S-* [JCTC2014]
Mg,Zn-* [JCTC2015-1]
Na,F,K,Ca,Cl,Br,I-* [JCTC2015-2]

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