[seminar] P. Lazić, 5.4. (srijeda) 14h (c.t.), seminar ZTF-a

[Anđelo Samsarov]

                SEMINAR  TEORIJSKE  FIZIKE


    (Zajednički seminari Fizičkog odsjeka PMF-a te Zavoda za teorijsku
     fiziku i Zavoda za eksperimentalnu fiziku IRB-a)

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    Van der Waals interaction on surfaces - three stories


    Predrag Lazić
    ZTF, IRB


    Datum:  srijeda, 5. travnja 2017.
    Vrijeme: 14 sati c.t.
    Mjesto: IRB, predavaona I krila


   Sažetak:

    Ubiquitous van der Waals forces might seem unimportant when compared to
much stronger chemical bindings. However in certain situations there are
rather unexpected effects caused by vdW interactions.

The first two systems include experimental and theoretical study of Cs
and Li atoms adsorption on graphene on Ir(111).

Graphene on Ir(111) surface is an interesting system because graphene
has almost pristine electronic structure in it due to its weak bonding
character to iridum surface.
The bonding is almost exclusively of the van der Waals type.

However adding Cs atoms graphene gets doped and nature of binding
changes - especially in the case when the atoms intercalate. Density
Functional Theory calculations with standard semilocal functionals (GGA)
- fail to reproduce experimental findings even qualitatively. Only when
the newly developed nonlocal correlation functional is used (vdW-DF)
which includes van der Waals interactions, are the calculations in
agreement with experiment, revealing the mechanism of graphene
delamination and relamination which is crucial for intercalation and
trapping of atoms under the graphene.

Iridium (111) surface has a very well defined surface state (visible as
a sharp peak in ARPES measurement). Addition of lithium atoms destroys
the coherence of the surface state resulting in vanishing of the ARPES
peak. This behavior is well known in surface science and is actually
used as a test for surface states. Surprisingly addition of the graphene
on top of lithium results in the restoration of the iridium of surface
state. Using the DFT calculations we discovered the mechanism
responsible for this, which seems to be quite general.

As the last system I will show as a one slide presentation an
explanation of the growth of MoS2 on the surface of the sapphire which
can not be resolved by standard DFT calculations due to the size of the
common unit cell. However simple vdW interaction calculation reveals
much more general picture of this type of systems.

Voditelj seminara: Anđelo Samsarov (asamsarov at irb.hr)

http://thphys.irb.hr/Seminar/list.htm
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