Howlers of the week 2005-2006
These are all genuine sentences and paragraphs that were written by students in their write-ups for the 2nd
year practical on High Temperature Superconductivity. Remember that spelling mistakes,
grammatical errors, and errors of logic are all entirely theirs, and have been reproduced
exactly as they appeared on the student's script.
- The actual configuration of the compound is octahedral, which is totally obvious from X-ray diffraction.
- The octahedral conformation stretches up and down.
- Another model, that is, not changing the oxidation state of copper must be changing the oxidation state of oxygen,
because no other elements are present in every other superconducting cuprate.
- As it is energetically more stable than the octahedral molecule but this is not the case due to steric effects, which outweigh the energetic effects,
and therefore in this molecule Cu forms a six coordinate bond with oxygen these bonds are not all of the same length due to the Jahn Teller distortion
effect the octahedral molecule will be stretched at the top and bottom.
- A simple model for superconductivity in this system is, in this model oxygen has been overlooked as it does not interact.
- The electrons will travel along the Cu layer and look for highly unstable Cu3+ ions while the electricity is applying on the
materials La2-xSrxCuO4. When a electron hit one of Cu3+ ions, it would repulse it. In such
way of electrons transporting there is no energy losing even in high temperature like 36 K. The rage of value of x also affects the
- The square planar structure is more electronically stable because one destabilising electron is stabilised by two stabilising electrons
which makes it lower in energy by ΔE so it is more stable than the octahedral structure.
- Normal conductivity comes accompanied by resistance.
- The blue orbitals “hanging” down from each Cu ion represents a d orbital with one electron in.
- La2CuO4 has a lattice structure with chains of cooper atoms each bonded to 4 oxygen atoms, it is therefore quite a uniformed structure and would
expect the cooper oxygen bond distances to be the same.
- The orbital from a neighbouring Cu2+ ion flips up...
- The Copper had a different and interesting oxidation state.
- The coordination number of Cu is now four and has adopted a square planar structure, which we know is what it actually wants to be.
- Once data points were put onto the graph and a rough x value for critical temperature was known and a curve line was starting to form, data points
where chosen to try a mirror the curve to see what kind of curve the data would produce i.e. was what being seen on the curve a maxima or minima of
the gradient or negative or positive point of inflection and the possibility of a poly hump curve.
- The red e represents the currant. This redcurrant moves along until it hits an ion.
- If x is a too large number, the material would not as energetically efficient because of the higher proportionate of defect Cu3+, and that there
would be less Cu2+ to start the process by losing an electron.
- The experiment conducted was designed to test a specific superconductor; Lanthanum cupperate.
- Liquid nitrogen is a relatively easily obtained substrate.
- This was a dry practical.
- As long as the electron jumps superconductivity will occur because there will be no nucleuses for it to collide with.
This means superconductivity is a battle of probabilities.
- The addition of a dope results in the atoms being changed.
- Superconductivity is when the resistance in a metal is equal to zero and hence there is no resistance in the metal.
- Superconductors now operate above the temperature of liquid nitrogen, which finally makes them useful.
- This is because of the Jahn Teller effect which is about how the square planar bonds in the octahedral stretches to make up the energy gap.
- I looked at the superconductor and it was p-type.
- The surrounding oxygen gives the copper its support.
- The electrons move between the rows of copper ions until they hit something, either a copper ion or an electron, or something else.
- I started the experiment by opening the window.
- But in octahedral 3e- are in high energy, so overall square planner is got a lower energy than octahedral but the octahedral is the complex structure
because of the steric effect. The structure becomes stretched (axial elongation is happening) to be something between octahedral and square planner which
is energetically favoured.
- The six oxygens feed electron density to the Cu3+ ion.
- Superconductivity is a property of superconductors.
- The lowest temperature that was used was 5 Kevins.
- Resistance arises when a travelling electron crashes into a Cu nuclei. When the Cu2+ next door bends its orbital towards it, the Cu3+ grapes an electron from the
- Oxidising Cu2+ ions gives rise to p-type supper conductors.
- The copper is octahedral and likes to be in octahedral.
- An example of High Tc superconductors are the cuprates based upon the Cu-O plane which has a particular high temperature when they superconduct
of what typically happens near absolute zero temperature but now happens at around 35K.
- The electron passes down a single layer of the Cu-O plane and as the coppers are vibrating they obstructs the electron and eventually the current diminishes as they
electron don’t have enough energy to skip between layers.
- The copper thus arrests the electron movement.
- The oxygens have been emitted from the diagram for clarity.
- La2-xSrxCuO4 exudes superconducting properties.
- The electron configuration is [Ar]3d94s0 so it has 9 d orbitals.
- Thus extrapolation was used to gauge reliability of the extreme results of great significance.
- Superconductors are substances which exhibit almost magical properties.
- Superconductors are known to have zero resistance flowing through them at temperatures near absolute zero.
- Less points were taken for straight lines, as less points are required to show a line; because there is no turning point.
- The electron passed to the Cu+2 ion next door. This is where the superconductivity comes from as it is a charge without effort.
- This lattice can keep the Cu+3 stable because of the oxygen atoms, which have a large electron density and can quench the usually unquenchable Cu+3 charge.
- However if there are too few the likely hood of an electron repelling a Cu+2 P orbital into electron pull of a Cu+3 ion is small.
- However, a Cu+3 ion is almost unimaginable!
- Conduction is caused by the mass migration of electrons.
- The experiment would then be run by selecting run.
- The plot was extrapolated mentally.
- Values of x were selected to ensure that a straight line was a straight line and to smooth out any curves in the data.
- Superconductivity occurs because something happens to either the copper or the oxygen, somewhere in the compound.
- At room temperature copper ions are vibrating quickly and cause fast diffraction of electrons when they collide.
- But the initial electron could hit the Cu core which is the origin of electron resistance. This is why x come into the story...
- A ‘virtual’ experiment was performed, using data which had been obtained by a long, expensive process.
- The electron encounters a repulsive orbital.
- In order to produce a smooth curve some of the points which were useless have been deleted.
- This means an electron will land on a Cu2+ instead of landing on a Cu3+.
- Before doping the copper oxidation state was +2, after doping it is 2 and a little bit.
- The copper Cu3+ badly wants an electron, so grabs one from the nearby orbital which is sticking out.
- The method for inserting extra oxygen atoms in the lattice is very dangerous as very large pressures are used while heating oxygen for a long time, which is very dangerous.
- The octahedral geometry tries to compensate by performing the Jahn-Teller effect.
- When there is no Cu3+ present the protruding orbitals of Cu2+ merely “swing” out of the way.
- Superconductivity is a new invention, and began when began when scientists reached temperatures of 5 K.
- Superconductors can hold a massive charge, which can generate massive currents and massive magnetic fields. So they can be used in things like trains and NMR machines, and other massive things.
- In this experiment no data was collected.
- The electron flowing through the plane will hit the empty d orbital.
- The electron flows down the Cu-O plane and bumps into some electron density or bash into the Cu2+ ions.
- When all the copper atoms are 2+ ions, the battery electron jumps across the lattice and eventually hits an electron. The electron repulsion knocks the travelling electron back and the orbital moves into an empty orbital.
- the travelling electron is abducted.
- This procedure was continued until the turning point began to turn.
- Cu has a decimal oxidation state.
- No values for Tc were found below 5K due to this being the melting point of helium, and therefore the material would have become submerged.
- The La and Sr cause steric effects due to their very large clouds.
- Cu3+ is a very rare element.
- the Cu can now happily form the square planar structure.
- This means they should be able to conduct forever as conductivity only ceases upon the crashing of the electrons.
- if that happened the Cu wires could be damaged and although theoretically a superconductor would have been produced, it would not actually have been.
- At x=0.15 it had reached the top of my graph, by 0.25 it had reached my bottom.
- Superconductivity begins because as the electrons in a Cu2+ d orbital move they come across the Cu3+ and are forced into the ion.
- This is a diagram of a 2D cut through section of the solid. The coordination number of each the octahedral copper atoms is 8 you can’t see the other two points as this is a 2D view. You would expect a ion to be square plainer but the number of oxygen atoms forces the copper into a octahedral forum to stabilise this forum the length of the Cu – O bonds take different lengths to make the cu atom feel more in a square plainer forum.
- This suggests that Cu+3 is present in this compound this is a highly unstable and will want to revert back to Cu+2 so it steels them from the surrounding Cu+2 atoms making it Cu+3 and so as an electron jumps from Cu atom to the next Cu atom (the fact that the electron has to stop at each atom is because the electron orbitals get in the way causes resistance) and a Cu+3 causes a Cu+2 to change this moves the orbital out the way of the electron and so causes ro resistance (superconductivity!).
- These strange solid that contain decimal atoms would be made from this kind of equation.
- The oxygen hangs in the middle like this. As the resign why this is a superconductor is that Earlyer we use Cu as the changing oxidation state but instead we could use oxygen. And the coordination is square planier.
- This suggests that the lower energy state is square planar. But when the molecule is drawn onto the computer however, the lowest energy complex is a six coordinate octahedral complex.
- Impedance in molecules is caused by an atom’s nucleus which will bring an electron to a halt if they get close enough.
- However, taking too many measurements will be seen as a waste of time.
- Hd1.9Ce0.1CuO4 is formed from Nd2CuO4 and CeO2.
- The conducted experiment was a success!
- As the electrons from the applied current moved down the chain they didn’t encounter any problems until they came into contact with a copper nucleus, which stopped them dead.
- this electron would be brushed upwards and be attracted so much by the Cu3+ ion, that it would become aroused.
- This showed that in this complex, the energetics won and the copper was square-planar rather than octahedral in geometry like what the La2CuO4 was. This fact was explained in the section above and the reasoning was written along with it.
- The whole experiment was logical and made great sense.
- This was calculated by interfering with the ratios of the atoms.
- There was a breakthrough fairly recently making a superconductor that functioned at 77K, which is the temperature of liquid nitrogen, which is a lot easier to make and find.
- There are 1.831 atoms of La, 0.069 atoms of Sr. If we multiply by 1000 there are whole numbers to deal with. Therefore the structure looks like La1831Sr69Cu1000O4000.
- The copper has changed charge from + 2 to – 2.2
- The superconductor was made from Lanthanium.
- The curve meets up with the x-axis is the Tc value we get.
- The electrons jump over orbitals on each copper ions (the orbitals cannot move but the electron can).
- In this case, the oxygen ion acts as an interstitial atom which is in the gap of the lattice cube and share electrons with many atoms/ ions around it, and so its oxidation number is reduced (and so does the ion).
- The superconductor was laced with Sr. The graph had to be extrapolated bellow 5K.
- For some materials the resistance decreases with lowering temperature as expected, until suddenly it disappears completely!
- Current can even jump small gaps, this is known as the Johnson Effect.
- This is the minimum number of points that satisfactorily depicts the curve; any more would be a waste of time and of no great use.
- The crystal has a copper oxide backbone.
- Extrapolation needs to be done, due to the physical impossibility of finding real readings for Tc at temperatures below the boiling point of helium.
- However the defect can only help the conductivity if the electron moving down the wire hits an electron in an orbital next to the defect, meaning that too few of the defects will have no
real effect for the electron would hardly ever hit an orbital next to a defect. Furthermore, too many of the defects would mean that the electron again would hardly ever hit an orbital next
to the defect, because there would be too few of them to have any effect. At small values of x, not enough Cu3+ will be around to facilitate the passage of electrons, and at
high values of x there would be too many Cu3+ to be of any use.
- The Cu3+ ion is desperate for an electron.
- High superconductors are compounds that superconduct at not such a low temperature.
- Below this temperature atoms freeze.
- No readings could be got below 5K. Conduction is via ‘holes’ in which electrons can go in.
- At high temperatures the Cu2+ ions become bigger.
- When an electric current is applied electrons are travelling along the ion plane in the lattice when an electric current is applied.
- The Meissner Effect allows for things like the maglev train in Germany. And the other one in Japan.
- Superconductivity takes place by empty orbital being able to overlap perfectly. By heating up a compound the position of the orbital is disrupted. The vacant position on the Cu that has had the orbital removed
is filled by the electrons moving across it so leaving no permanent effect.
- If this experiment were carried out in the lab without the use of the computer program, the experiment would take a very very long time.
- So I first ran the experiment at 0 and then 1. These values gave no superconductive properties, so then I looked at x being 0.5, and again no superconductivity.
I then looked at 0.1, this gave a superconductive reading on the graph. So then, various points where investigated in the region of 0.1 until a curve formed.
- With the development of self levitating trains reducing traffic and power cables that do not loose great deals of electricity due to resistance, we could well see
a far cleaner future.
And one from Theoretical workshops...
- The process starts with the two molecules binging in proximity.
And another one from this year's exams ...
- The Langmuir isotherm assumes that the surface is flat and humongous.
And one from the library project...
- Most diabetics are trained to recognise this and can solve the problem by eating something sweet, like the picture opposite.