Leaving Assignments To Love Brexit

Top 10 ways to write a personal narrative 5 best ways to answer why medicine

In general it is possible to note that conductivity of monocrystals and films of C60 at contact with oxygen quickly (for some) goes down on 3 — 6 orders while the exposition in the atmosphere of argon, nitrogen and helium has no impact on a. Spectral dependence of photoconductivity of films in an of oxygen qualitatively coincides with photoconductivity of oxygen-free films, but absolute values are significantly lower. Properties of films are practically restored at a in vacuum up to the temperature of 160 — 180 °C. However the with oxygen in the presence of lighting leads to changes in conductivity: its value at the room temperature falls to 10^-14 (Om.sm) ^-1, and activation energy increases to 95, i.e. is close to a half of a zone. Influence of oxygen on conductivity and photoconductivity of fulleren of C60 and C70 most often is explained by that interkalirovanny oxygen creates the deep lovushechny levels for of a charge located at the level of 7 edges of a zone of conductivity are lower. Influence of oxygen on conductivity also by creation of the disorder potential which electronic states at edges of HOMO — LUMO. At illumination of samples oxygen enters chemical reaction with formation of S-O - communications.

It is possible to allocate at least 4 various orientation conditions of a fullerit of C60: a glass phase, a simple cubic lattice, a phase of free rotation (most often face-centered cubic, however messages about hexagonal dense and the polymerized phase met.

t1u. Calculations show that fullerit C60 in the GTsK-lattice represents the pryamozonny semiconductor with a minimum of a power crack in a point of the X zone of Brillouin. Calculations in approach of quasiparticles predict the size of a crack 15, the method of local density gives obviously underestimated value 5. As the most reliable value for power distance between the middle of the zones HOMO and LUMO it is possible to consider 36 at theoretical value 3. Ionization potetsiat it is equal 62, affinity to an electron 65, energy of the lowest tripletny state 7. Work of an exit for amorphous films of C60 is defined as 53. Coulomb interaction between molecules makes

orbitals (HOMO — LUMO) in C60 (both in the isolated molecule, and in the condensed state) lies in the optical range. The first detailed theoretical research of electronic structure of C60 in a solid-state state was executed by Saito and Oshiyama. Physical properties of a molecule are defined by its electronic structure, and in this regard C60 has no analogs. In a molecule of C60 there are 60 pi-electrons which are in the least connected states and, thus, define how C60 will contact other atoms or molecules in a firm state.

Now the set of the experimental and theoretical works devoted to various aspects of physics of C60 in various states is published: the isolated molecule, C60 in solutions and especially C60 in a solid-state state. At temperatures below 600K C60 forms molecular crystals. Crystals of high purity (998%) and the millimetric sizes can be grown up from a gas phase. Let's call fullerenam the isolated molecules of Cn, a fulleritama – a fullerena in a solid-state state, including the polymerized fullerenovy structures. Also interkalirovanny connections and endoedralny fullerena belong to diverse fullerenovy derivatives. At intercalation of impurity are entered into emptiness of an uristallichesky lattice of a fullerit, and endoedralny fullerena are formed at introduction of atoms of various grade in Cn cluster.

in an elementary cell. Transition is not connected with movement of molecules, and caused only by mutual streamlining. The rotary motion is replaced by the spasmodic and libratory movement about equilibrium orientation. At a temperature of 90 To jumps freeze and there is a transition like vitrification. Orientation of molecules influences such lines of electronic structure as degeneration, dispersion, width of zones, the provision of extrema of a valent zone and zone of conductivity.

Subsequently there were works, experimentally emergence of covalent communications between fullerenovy. It was shown that C60 can be turned about other structure under the influence of high pressures and temperatures. The structure of this substance was defined as with parameters of a lattice and = 22 A and with = 26 A. The distance between molecules in such phase approximately equaled communication that means possibility of formation of communications between molecules.