4th EucheMs chemistry congress

tuesday, 28-Aug 2012
s813
chem. Listy 106, s587–s1425 (2012)
Physical, theoretical and Computational Chemistry
theoretical Chemisry – i
o - 2 3 2
reCent exAMPLeS on reLAtiviStiC effeCtS in
CheMiStry
P. PyyKKo 1
1 University of Helsinki, Department of Chemistry, Helsinki,
Finland
Relativistic effects often explain the special properties of
6th-Period elements (Cs-Rn), as compared to their 5th-Period analogues (Rb-Xe). It was recently shown using solid-state
calculations that about 80% of the voltage of the lead-acid battery
come from relativistic effects. [1] Cars start due to relativity. For the
mercury battery, the corresponding contribution is about 30 %. [2]
The form of the periodic table up to Z = 172 was recently
reconsidered using average-of-configuration Dirac-Fock
calculations on atoms and ions. [3] The last valence electron left
upon ionisation was used to classify the chemical group to which
the element should be assigned. Two recent reviews have been
compiled, one on the fundamental, mainly QED aspects [4] and
another on chemical properties, influenced by relativity. [5] As
discussed there, more information is now available on spin-orbit
(SO) effects in structural chemistry. The relativistic origin of the
yellow colour of gold is now confirmed. The use of quantum
chemistry to predict new, simple inorganic species was also
reviewed. [6]
references:
1. R. Ahuja, A. Blomqvist, P. Larsson, P. Pyykkö and
P. Zaleski-Ejgierd, Phys. Rev. Lett. 106 (2011) 018301.
2. P. Zaleski-Ejgierd and P. Pyykkö, Phys. Chem. Chem.
Phys. {\bf 13} (2011) 16510.
3. P. Pyykkö, Phys. Chem. Chem. Phys. 13 (2011) 161.
4. P. Pyykkö, Chem. Rev. 112 (2012) 371.
5. P. Pyykkö, Ann. Rev. Phys. Chem. 63 (2012) 000.
6. P. Pyykkö, Phys. Chem. Chem. Phys., Advance Article 1
February 2012, DOI: 10.1039/c2cp24003c.
Keywords: Relativistic effects; heavy-element chemistry; Gold;
lead; quantum chemistry;
theoretical Chemisry – i
4 th EucheMs chemistry congress
o - 2 3 3
why Are the interACtion enerGieS of
ChArGe-trAnSfer CoMPLexeS ChALLenGinG
for dft?
S. SteinMAnn 1 , C. PieMonteSi 1 , A. deLAChAt 1 ,
C. CorMinBoeuf 1
1 Ecole Polytechnique Federale de Lausanne, Institute of
Chemical Sciences and Engineering, Lausanne, Switzerland
The description of charge transfer complexes by standard
density functionals is highly challenging. [1] Illustrative examples
include large overestimation of charge transfer by local and
semi-local functionals and inaccurate binding energies in the
ground state. We demonstrate that standard density functionals
fail to accurately describe interaction energies of charge-transfer
complexes not only because of the missing long-range exchange
as generally assumed [2] but mostly because of the neglected
ubiquitous dispersion interactions. [3] Accounting for the missing
dispersion interactions is thus of key importance. These assertions
are based on the evaluation of the extent of stabilization due to
dispersion using both DFT coupled with our recent
density-dependent dispersion correction (dDsC) [4] and high-level
ab initio computations and reflects the imperfect errorcancellation
between the overestimation of charge-transfer and
the missing long-range interactions. An in-depth energy
decomposition analysis of an illustrative series of 4 small
ambidentate molecules (HCN, HNC, HF and ClF) bound
together with NF provides the main conclusions which are
3
validated on a typical organic charge-transfer complex
(i.e., tetrathiafulvalene-tetracyanoquinodimethane). Only
well-balanced functionals such as PBE0-dDsC, LC-BOP-LRD
and M06-2X can overcome the difficulties of standard density
functionals for charge transfer complexes. These results parallel
the benchmarking on 341 diverse reaction energies where these
functionals were among the best hybrid density functionals. [4]
references:
1. Ruiz E., Salahub D.R., Vela A., J. Am. Chem. Soc. 1995,
117, 1141.
2. Sini G., Sears J.S., Bredas J.-L., J. Chem. Theory Comput.
2011, 7, 602.
3. Steinmann S.N., Piemontesi C., Delachat A., Corminboeuf
C., J. Chem. Theory Comput., doi 10.1021/ct200930x.
4. Steinmann S.N., Corminboeuf C., J. Chem. Theory
Comput. 2011, 7, 3567.
Keywords: Density functional theory; noncovalent
interactions;
AUGUst 26–30, 2012, PrAGUE, cZEcH rEPUbLIc