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Quantum engineering

  1. Feb 11, 2004 #1
    when it comes to building buildings, triangles are the strongest shape. so i would of thought triangle based molecules would be the strongest, but diamond says other wise. what am i missing?

    also, when it comes to armor, i know 2 layers of 1 inch thick gives more protection than 1 layer of 2 inch thick, if there is a space between the two. but surely theres a limit of how many layers i can have before the space between each layer is too small to matter, and the thickness becomes like tinfoil. so would 1000 layers of tinfoil give better protection than the same width as a single layer? (asuming the tinfoil was made from steal)
     
    Last edited: Feb 12, 2004
  2. jcsd
  3. Mar 2, 2004 #2
    Yes, Gara, an interesting question about the diamond lattice. As you say, triangles are not the strongest shape, they are the only strong shape.

    I wish some smart person would enter in here and explain the non-bending nature of the carbon-to-carbon bonds in the diamond molecule since the entire structure looks like mighty poor architecture.

    I also like your question about walls.
     
  4. Mar 2, 2004 #3
    thanks. you know, this part of Physics Forums sure is queit.
     
  5. Mar 2, 2004 #4
    Diamonds are one big network of covalently bonded carbon. That explains its strength.

    The thing to remember is that diamonds are susceptible to cleavage along certain planes with an adequately strong enough blow, so it's not like there are no weak points with diamonds. Most applications (including jewelry settings) are intended to prevent such cleavage planes from being exposed. These planes are subject to the structural symmetry, so ultimately all extended lattices of a material should be suspectible to cleavage to varying degrees.
     
  6. Mar 2, 2004 #5
    A revised explanation for the hardness of the diamond molecule:

    Click:
    Diamond lattices; two versions
     
    Last edited: Mar 3, 2004
  7. Mar 3, 2004 #6
    so could we make man made molecules that are triangles?

    and as for that link, i only confuses me more :(
     
    Last edited: Mar 3, 2004
  8. Jul 21, 2004 #7
    There are molecules, and there are crystals. I believe we should be speaking about crystals in this case, which can be seen as many identical molecules, packed together in an ordinate manner.

    Many crystal structure, including diamond, can be seen as triangular-based, but in three dimensions.

    Imagine packing billiard balls in a box. Any three balls that are close by will form a triangle. Crystal structures are often, but not always, packed this way.
     
  9. Jul 21, 2004 #8
    For diamonds the atoms are arranged like tetrahedrons, which are the three dimensional equivalent of triangles, and yes, that is one reason diamonds are so hard, the tetrahedral arrangement is rigid and incompressable.
     
  10. Jul 22, 2004 #9
    Not to confuse things, but I have my own two cents (and confusion):

    Isn't diamond an unstable formation of carbon at everyday temperatures and pressures? I thought that graphite was the more stable form (at these temps and pressures) so if graphite is more stable, why should diamond be more resistant to pressure (i.e. hardness)? Does the stability of a carbon phase have anything to do with the strength of its structure? I guess I am wondering if the Gibbs free energy of each of these phases has anything to do with crystal strength.

    Sorry, I didn't have two cents...just confusion :confused:
     
  11. Jul 23, 2004 #10
    Yes, you are correct - graphite is more stable than diamond at room temperature and atmospheric pressure. But the stability of a material has nothing (or very little) to do with its strength or other physical properties. While the physical properties arise from the structure of the material, its stability arises from the energies associated with the electon configuration that creates that structure.
     
  12. Jul 24, 2004 #11
    In other words, at atmospheric pressure and temperature, you are more likely to see diamond spontaneously turn into graphite, than you are likely to see graphite spontaneously turn into diamond. Although we don't see much of either...
     
  13. Jul 24, 2004 #12
    In diamond the atoms are in a rigid interlocking structure, in graphite the atoms are arranged in layers which can easily slide over each other. That is why graphite is so slippery and makes a good lubricant.
     
  14. Jul 24, 2004 #13
    Isn't bond structure related to energy? I thought that nature desires to minimize energy and that was the reason for the way molecules form bonds. From this I figured that bond structure (molecule geometry) would be dictated by energy. Are strong geometric molecule shapes just not stable from an energy standpoint?

    For example: It is difficult to compress or shatter steel (ie hit it with a hammer), but most natural rocks (say quartz) tend to break or fissure under these kinds of stresses. Does this mean that steel would have a strong geometric molecular shape but is not consist of an energetically stable crystal lattice, while quartz would be more stable but be less structurally vigorous? Forgive the (potentially) bad examples, I wish I knew more about materials, but that is why I am here.
     
  15. Jul 25, 2004 #14
    when it comes to building buildings, triangles are the strongest shape.

    On a discontinued website I proposed that vacuum is responsible for bonding partly on the bases that the strongest bonding force per unit is acheived with an equalateral triangular pyramid because that is the largest number of units that can be assembled without any unit being shielded from the centre point of the vacuum.
    Your diagram is an assembly of triangular pyramids. So also is the newly discovered pentaquark, but in pentaquarks the base is shared by two pyramids; due to the pressure of the bonding force field. (It is bonding force field pressure that prevents the assembly of more than three quarks and centrifugal force (spin) that stretches the quark triangle bonding field to allow the creation of a pentaquark).
    It is common practice to attribute bonding to an undefinable force (magnetism) that then has to be sub-divided into 'attractive' and 'repulsive' forces; or where there are no electrons, bonding is attributed to 'bonding particles' that have to perform some weird movements to do the job. This ridiculous situation will persist as long as there is a strong resistance to acknowledging that all these forces can be replaced by vacuum. Does it not strike you as peculiar that those developing gravity and string theories place great weight on vacuum while those studying particles, atoms and forces refuse to even consider the possibility that all forces are simple combinations of vacuum and density.
    Your diagram would be the one used by vacuum theorist and the top four units are the same as the diagram I used to explain atomic vacuum bonding. Each face of the pyramid is the same as the diagram I used to explain quark vacuum bonding.
     
  16. Jul 25, 2004 #15
    when it comes to building buildings, triangles are the strongest shape.

    On a discontinued website I proposed that vacuum is responsible for bonding partly on the bases that the strongest bonding force per unit is acheived with an equalateral triangular pyramid because that is the largest number of units that can be assembled without any unit being shielded from the centre point of the vacuum.
    Your diagram is an assembly of triangular pyramids. So also is the newly discovered pentaquark, but in pentaquarks the base is shared by two pyramids; due to the pressure of the bonding force field. (It is bonding force field pressure that prevents the assembly of more than three quarks and centrifugal force (spin) that stretches the quark triangle bonding field to allow the creation of a pentaquark).
    It is common practice to attribute bonding to an undefinable force (magnetism) that then has to be sub-divided into 'attractive' and 'repulsive' forces; or where there are no electrons, bonding is attributed to 'bonding particles' that have to perform some weird movements to do the job. This ridiculous situation will persist as long as there is a strong resistance to acknowledging that all these forces can be replaced by vacuum. Does it not strike you as peculiar that those developing gravity and string theories place great weight on vacuum while those studying particles, atoms and forces refuse to even consider the possibility that all forces are simple combinations of vacuum and density.
    Your diagram would be the one used by vacuum theorist. Given that each circle represents a sphere then the top four units are similar to the diagram I used to explain atomic vacuum bonding. Each face of the pyramid is similar to the diagram I used to explain quark vacuum bonding.
     
    Last edited by a moderator: Jul 25, 2004
  17. Jul 25, 2004 #16
    Yes, you are correct. But a function (enegy in this case) can have local minima as well as a global one. Any structure would have to be at one of those minuma to be stable, but since one local minimum can be higher than another, thecorresponding structure can still be less stable than a different one.
    I'm not sure. I think the two are quite unrelated, so you can have any combination, but I don't know any examples where a more stable structure is also more rigid. In any case, the hardness of steel comes not from its underlying crystal structure (that of iron), but rather from the carbon atoms that polute the crystal, making it harded for dislocations to move (moving dislocations is what allows for plastic deformation). I hope this reply won't confuse you too much, as it contains some technical terms...
    Not really. Vacuum and density *cannot* explain such forces, since density is not even applicable unless you have at least several particles. And yet, When you have just two particles - a proton and an electron - they still attract to form hydrogen, despite the fact that you cannot talk about density in this case. And as for vacuum alone, it doesn't do much either, since there is vaccum all around.
    I'll give you one thing though, it may be possible to explain gravity with vacuum flactuations, but gravity is far too weak to be involved in the formation of hydrogenm for example.
     
  18. Aug 1, 2004 #17
    Not really. Vacuum and density *cannot* explain such forces, since density is not even applicable unless you have at least several particles. And yet, When you have just two particles - a proton and an electron - they still attract to form hydrogen, despite the fact that you cannot talk about density in this case. And as for vacuum alone, it doesn't do much either, since there is vaccum all around.

    Are you saying that particles do not have density? Then how do they have mass?
    What is the attractive force? The standard answer is magnetism yet on this very question no one has been able to answer my questions on ionic and isotope radii on any of the forums. (Most recent question is currently on the Chemistry forum, having drawn a blank on Quantum and Atomic forums).
    You dismiss vacuum, but I recall reading that according to QT, the force of vacuum in the void is the greatest force known to man.
     
  19. Aug 1, 2004 #18

    selfAdjoint

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    The electron has mass, but no well defined radius that anyone can find. So its density is undefined; the numerator is well known but the denominator is not. The dumb answer "infinite density" is certainly wrong. And the slightly less dumb idea of using the compton wavelength for the radius has not produced anything uselful as far as I know.
     
  20. Aug 3, 2004 #19
    Anyone know an answer to my second question about armour?
     
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