Re: My New Website

From: Y.Porat (maporat_at_012.net.il)
Date: 06/17/04 

Date: 17 Jun 2004 03:11:01 -0700

"Lothar Brendel" <l.no.spam.brendel@uni-duisburg.de> wrote in message news:<2j4utpFruudgU1@uni-berlin.de>...
> Y.Porat wrote:
> > "Lothar Brendel" <l.no.spam.brendel@uni-duisburg.de> wrote in message
> news:<2j3h6bFt99t0U1@uni-berlin.de>...
>
> [...]
>
> > another anyway:
> > in the figures that you brought above
> > ther is not a single quantitive munber.
> > ie there is not the numerically value of 'a'
>
> That's because diamond is not the only material with a diamond lattice. And
> each one has a different "a".
---------------
you saied that a is something (to lazy to look for it...)
something around 3.5 A
so i would like if it is based on the Xray findings
if i am not wrong acording to Bjoerns data and calculations
it is about 4.5 A .

and btw do you know a sourse of those data
that will tell us about measurments of different crystalls
or methat latice as measured (not as computed like by the
specific weight etc just measured without additional
assumptions!?

>
> [...]
>
> > now may be i will alow Bjoern (just in this case
> > to scann the figures that i constructed with my poor devices
> > and you could see that it is exactly the figures you provided.
>
> Why don't you just look at http://www.trustphotosite.com/Lotta/Tetrahedrons
> and check whether it's what you have in mind.
---------------
i looked at it
and dont know why it gives nothing but sort of starnge commercials???
---------------------
>
>
> > actually as i sayed:
> > a thtraheder as a base unit can produce only *one* 3d structure!!
> > that is what you quoted
> > in that asructure **all** the 'arms' (ie electrons) are ocupied
> > by building that structure *no free arms left for other activity.
> > i called it 'the close compact hexagonal ' structre
> > it is not my name i took it from one of my old books
>
> But you misunderstood something there. In the hexagonal closed packed (hcp)
> structure there are 12 nearest neighbours, not 4.
--------------
no the structure i mean has only 4 atoms aroung a junction
because .... a tetreheder had only 4 'arms'
i doubt if we talk about the same thing
if you take for instance the iron structres it has 4+4 arms
ie althogether 8 around each junction
an and i thing if i am not wrong it is interesting to assert it
you will never fing more than 8 arms per atom !!!!
(though the 'shell model' gives you a 'supermarket of possibilities'
of electrons around the atm coming in or'out' you just name it...
in crystal latices in contradiction of that 'large degree of freedom'
you will fing never more than 8 around an atom, why not more ?.....!!
---------------
>
> > anyway the name is not the issue
>
> When discussing with other people, you should stick to the terms commonly
> agreed on.
>
>
> > so again i cant see how one can 'add' something more in it
>
> Though fcc can be obtained from packing spheres close, not every fcc
> structure must be very dense; i.e. the obejcts sitting at the lattice points
> don't need to touch each other.
--------------
the atome never touch each other it is those 'arms' that thouch.
anf it it does not touch it contributes nothing to its strength.
a strong crystal or metal latice cannot 'aford' arms that not
all of them used for the perpous of strength bondind
the diamond is the harder '*mainly* because all its arms
are 'working' no 'lazy bones' there
---------------
>
>
> > what takes mt attention is that 'interpenetrated structure'
> > that you showed -is at the end of the day....
> > the same 'close compact hexagonal' that i myself take as the
> > diamond structure
>
> If you drop the 'close compact hexagonal', which is reserved for a different
> lattice (namely hcp), I can agree.
>
>
> > the only question now is what is that 'a' that is quoted there
>
> Depends on the material. For diamond a=3.57 Angrstoem.
--------------
where from di dyou take it?
----------
>
>
> > btw in another figure that Bjoern bgought for Silicon
> > (there is there even a short 'exercice' of calculation what is the
> > density of silicon'
> > they get there a resuly of :
> > 5 x exp 22 atome per Cm^3
> > and not the 1.7 exp 23 per Cm^3
> > which is 3 times less dence. worth thinking about.
>
> If you think long enough, you will find out that's because carbon and
> silicon are _different_ elements. Why should they have the same density?
>-----------------
just to reveal you one of my findings is that ......
you can build *all of them* with only *one* arm length!
(hope i am right...) please dont forget where have you heared about that
nonsense for the first time. i want a copyright about it (;-)
-----------------
----------------
>
> > > Do you agree with the structure shown in
> > > http://www.trustphotosite.com/Lotta/Tetrahedrons, given that each
> > > tetrahedron contains another atom in its center?

as isayed i saw nothing but commercials there
> > -------------
> > if it was my school who am i to resist .........
>
> So, that's your criterion for quality?
not nessesary i just noted my nostalgy for my old good school
(actually in my nostalgy i try to forget the hard days and nights
they gave me ....... that swhy it is a good school ...)
-----------
>
> BTW: http://www.trustphotosite.com/Lotta/Tetrahedrons is different from
> http://phycomp.technion.ac.il/~nika/diamond_structure.html. Obviously you
> are too lazy to even click on links. That's tough!
-----------
see above

>
>
> > > >(that belongs as well to say the benzen-
> > > > and the benzen is a liquid!)
> > >
> > > How do you relate the tetrahedron to benzene? There are no more 109°
> angles
> > > but lower symmetry, electron delocalization and that stuff.
> > actually it is not only benzen
>
> Hello? Benzen does _not_ have 109° angles!
-------------
are you sure it is not a 3d tetraheder based structure?
-----------
>
>
> > my old chemiastry book tells me that it is typical to many
> > organic compounds!
> > they even call it there 'the cradles and 'armchires'
> > *ie 3d structures* that fit exactly the struccture that you
> > *and me* are refering to.
>
> I strongly doubt that many organic crystals have a diamond lattice, but I
> won't elaborate that here.
it is not th multy structure it is just one 'ring' hexagonal ring
why and how just one i dont know at this moment.
may be because of other atons involved there like hydrogen ?
but from my 'experience' hedrogen atoms use usually is
'fillers' not as 'structure makers'
-------------
---------------
>
>
> > btw i found in the srtucture that i built in my oun hans
> > that surprisinly enough:
> > if you look ast it from one specific angle you see not those
> > beautiful hexagons but ... rectangles!
>
> Big surprise... You should actually see _squares_, namely the faces of the
> fcc conventional unit cells.
-----------
yes after knowing it - it is not a surprise .....
but before ? nothing in a tetraheder reminds a rectangle. 

----
> 
> 
> > for me at least it explained the structure of say 'Calcite'
> > that lokes like  - if you look at it sideways like a rectangle
> > but if you 'cross sect it' you get an exagone
> > so it all fits to that same 3d structure
> 
> It's _not_ the same 3d structure! Calcite does _not_ have a diamond lattice,
> it's trigonal, cf. e.g.
-----------
????
> http://home3.netcarrier.com/~chan/SOLIDSTATE/CRYSTAL/calcite.html.
> --------------
i cant click it..
--------
> 
> > that is the only possible result of a teraheder as base building unit.
> 
> Why do you think Calcite had a tetrahderon as unit cell?
--------------
i am speaking about waht you called the 'primitive unit cell'
all atoms has either two or four arms at their front pole'
and others at their 'back ple'
if only 2 in front anf 2 at back are active
you have a tetraheder.
and if i am not wrong in the calcite you have hexagons
if you look at it from a somecific angle. (cross section)
-------------
> 
> 
> > and i cant see hoe one can add into it atoms that 'no one can care
> > for them' in that above structure,
> 
> Lattices do not have atoms, they have lattice points, for which nobody has
> to take care.
---------------
i dont care too much about hypothetic 3d structures
*fo rme what counts is only **real structures of nature**
and the striking fact to notice is 
*that the number of actual structures is **less** than all the 
possible 3 d structres
i strongly recommend that you will keep it in your memory
because it is .... very meaningfull!.
-------------
> 
> 
> > and in addition to get
> > the most solid structure of the diamond
> > but after all that it is possible that i am missing something
> > (missing some important 'catch' in it?
> 
> Firstly, you are missing that not all cyrstal have a diamond lattice.
----------
thanks i know it there is the iron st4ucture
there is the Na- Cl sructure and others
but a i saied abouve , much less sorts than expected
by stereometry and the 'shell model' .....
and it i svery meaningfull.
ok i will not keep you in tension
fo me atleast it is one of the *disprovals* of the shell model!!
of say 80 electrons around the atom!!.
-------------
-----------
----------
--------------
> 
> Secondly, and more important, you seemingly cannot abstract from a crystal
> (physical object) to a lattice (mathematical object).
---------------
i dont know what you mean by abstract
but i know the difference between theorethic and realistc.
i didnt know untill you told me that latice is only theorethic strructure.
thanx
-------------
> 
> 
> > > > how is it possible that one can 'interlenetrate ' anything more
> > > > in it to get something denser?
> > >
> > > Okay, if  by "bonds" we refer to the nearest neighbor distance of  1.54
> > > Angstroem, then each of the fcc lattices (which are going to be
>  interlaced)
> > > doesn't contain any "bonds" at all.
> > ------------------
> > ?????????
> > vbey questionable!
> 
> Not at all. If you remove the cyan "atoms" in figure 1 of
> http://phycomp.technion.ac.il/~nika/diamond_structure.html (which belong to
> the "other" fcc lattice), you have cut all the "arms".
-------------
no arm bonds 'no money' :-)
again a could not see it .
-------
> 
> 
> > > In each of the two lattices, we have
> > > only "empty" tetrahedrons (i.e. the central atom is missing, since it
> > > belongs to the other fcc lattice), and hence the neighbor distance in
>  each
> > > fcc lattice is 2.52 Angstroem, namely the base length of the (empty)
> > > tetrahedrons.
still not clear to me 
> > -------------
> > how comes that ';empthy tetrahedron' while it should be
> > the atom that is the base for all that story?
> 
> As I explained: "Empty" means, there is no _central_ "atom" in the
> tetrahedron, but there are some on its vertices.
-------------
??????
-----------
> 
> More important: When discussing _lattices_, it's not the _atom_ that is the
> base "for all that story". Lattices are mathematical objects which one could
> happily discuss and analyse even if crystals wouldn't exist at all. But
> studying lattices is very _useful_ because actually there are situations
> where atoms (or rather primitive unit cells) like to arrange on lattice
> points.
--------------
 sorry i am not interested at all in hypothetic structures.
----------
> 
> 
> > and who can ;lend it' elctrons while all of them are 'locked' by their
> > other ocupation of buildind the base sructure
> > and all the other electrons are preocupied by the 'less dense' structure??
> 
> Try to understand the difference between "lattice" and "crystal". As I
> already explained, nobody assigns a physical meaning to each of the diamond
> lattice's sub fccs.
-----------
ok i undestood there is a difference
but i dont buy hypothetic structures
only rock solid proven structures with no 'in fillings' 
by immagination of missing parts or ununderstanable parts.
actually the best thing could be 
may be gama rays 'direct ' pictures if possible ??
----------
--------
> 
> > but afik Xenon has mor eelectrons than Carbon
> > so is it possible that in that case those aditional electrons
> > instead of being more capable of buildind something better
> > are 'rather disturbing' ??!! an interesting question again!
> 
> No. Not "disturbing" but "closing the outer shell" (as one learns in
> chemistry). That's why Xenon is not very reactive. Gosh, read a book!
-------------
Gosh i ead books (and muy book) and became convinced
that people(even the book writers) are just inmost cases 'hand waving'IOW 
they dont know how much they dont know !!!
and just parroting
---------
-----
 all the best
Y
-----------------

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