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3ob-X-X
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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 super-
sedes 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].

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The following parameter should be generally used for DFTB3/3OB
calculations:

zeta = 4.00 (gamma^h function exponent; DampXHExponent in DFTB+)

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List of all atomic Hubbard derivatives (atomic units):
Br = -0.0573
 C = -0.1492
Ca = -0.0340
Cl = -0.0697
 F = -0.1623
 H = -0.1857
 I = -0.0433
 K = -0.0339
Mg = -0.02
 N = -0.1535
Na = -0.0454
 O = -0.1575
 P = -0.14
 S = -0.11
Zn = -0.03

Maximum angular momenta for calculation input files:

Br = "d"
 C = "p"
Ca = "p"
Cl = "d"
 F = "p"
 H = "s"
 I = "d"
 K = "p"
Mg = "p"
 N = "p"
Na = "p"
 O = "p"
 P = "d"
 S = "d"
Zn = "d"

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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

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Relevant Publications
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[JCTC2013] J. Chem. Theory Comput., 2013, 9, 338-354.
[JCTC2014] J. Chem. Theory Comput., 2014, 10, 1518–1537.
[JCTC2015-1] J. Phys. Chem. B, 2015, 119, 1062–1082.
[JCTC2015-2] J. Chem. Theory Comput., 2015, 11, 332–342.