Re: graphene

Dear Arkan,
can you please explain us what would you exactly need to simulate such a way that we will be able to address your request in a
better way?
What is your exactly your problem (source particle, geometry etc...).

I don't understand your statement "According to my search Carbon and graphene has same density" please give me a reference.

The exact density of a material depends on many factor. The density of carbon varies from 1.8-1.9 g/cm3 for the amorphous state to
about 3.5 g/cm3 of the diamonds. It's up to you to define the correct density of your newly defined material starting from the
measurement you perform or to the specification you got from the company who will produce your graphene layer(s).

  From the material point of view Graphene is closely related to Graphite (rho~ 2.1-2.2 g/cm3). When graphene sheets (hexagonal
lattice with separation of 0.142 nm) stack you form - as a matter of fact - graphite. So I would rather go for the density of pure
graphite than the one of amorphous carbon. Things are changing dramatically for graphene composites.

The density is macroscopic quantity and express the (average) mass per unit of volume of a material, so for energy deposition
studies it's more important to define correctly the substrate or the absorber material rather than few layer of graphene (max some
nanometers of material).

A similar approach (I mean to model well the radiation deposition in the absorber) was used to study GRD (Graphene Radiation Detector)
in this little paper http://www.physics.purdue.edu/quantum/files/GUARD_IEEE_Proc_Foxe.pdf
I've see also a couple of nice posters (probably by the same students) about this types of work at the IEEE NSS/MIC in 2010 in
Orlando but I can't find the links.

Graphene is a mono-layer material and it's mechanical and electronics properties are valid for a single layer. If you have two layer
the material change slightly properties and it's called bi-layer graphene. Multi-layer graphene
(http://sciencewatch.com/ana/st/graphene/rfmap2/) properties are not completely known yet.

I would be amazed if you could find by the way a company who would be able (today) to produce large and thick multi-layer graphene
plate. Normally you use a substrate and you grow by CVD or PECVD your layers one by one.

Modifying the Sternheimer parameters means you modify the ionization potentials and density effect parameters, so you need to know
what you place there. To my knowledge nothing has been measured or calculated yet for graphene.

Probably you already those paper:
http://rmp.aps.org/abstract/RMP/v81/i1/p109_1
http://jcp.aip.org/resource/1/jcpsa6/v128/i19/p194701_s1?isAuthorized=no

Cheers
Vittorio

On 07/08/2012 16:23, Ertan Arikan wrote:
> Dear Fluka Experts,
>
> According to my search Carbon and graphene has same density.
> I wonder how FLUKA can distinguish graphene and carbon if they have same thickness (for example 5 mm)?
> Are the STERNHEIMEr parameters same both of them?
> Is the MAT-PROP card required for graphene ?
> For the thin material how electronic equilibrum can be obtain ? (Potugal 2010 lecture is not enough for me, I could not undestand it
> )
>
> Thanks in advance
> Best Regards,
>
> Ertan ARIKAN
>
>

-- 
Dr. Vittorio Boccone - University of Geneva
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