Final writing exercise Essay

There be three phases whereby separately has a different quartz glass structure at three different temperatures. At room temperature (298K), mannikin III is register whereby Cs3H(SeO4)2 has a lechatelierite structure of a monoclinic with a musculus quadriceps femoris group of C2/m. At 400K, Phase II is act whereby Cs3H(SeO4)2 has a crystal structure of a monoclinic-A2/a rest. At 470K, Phase I is present whereby Cs3H(SeO4)2 has a crystal structure of a trigonal with a musculus quadriceps femoris group of R3-m. In Phase III, as we brush off see in Figure 2(a), the pose of the tetrahedrons is mate to the a- bloc, and in amongst these SeO4 tetrahedrons argon the atomic number 1 hampers. Looking at a 2dimensional perspective, we can as well see that on that point is a translation exercise of the SeO4 tetrahedrons along the a-axis hence the con fakeity agent would be a glide line parallel to a-axis. In a 3-dimensional perspective, we can see that Phase III has a 2-fold rotation axis and contains glide planes.In Phase II, from Figure 2(b), we can see that the positioning of the SeO4 tetrahedrons are along the approximate mode 310. Observing the schematic of the crystal structure in Phase II, we can see that there is a vertical mirror line in between the SeO4 tetrahedrons. There is besides an a-glide reflection vertically. In Phase I, from Figure 2(c), the positioning of SeO4 tetrahedron is similar to that of Phase II, however the difference is the crystal structure and the heat content bonding. Comparing both(prenominal) Phase II and Phase III crystal structures of the compound, Phase II contains two-fold screw axis, inversion center and a two-fold rotation axis, which is the sole conclude for Phase II to be twice of that of Phase III in terms of geometrical arrangement of heat content bonds.From the above analysis of the symmetry of the crystals structures in different phases, we can tell that Phase III has the nearly symmetry operato rs and hence achieving the highest crystal symmetry generating a first gear geometrical arrangement of total heat bonds. Due to the low geometrical arrangement of hydrogen bonds, the mobility of protons decreases giving the result of ferroelasticiy. The drastic change from superprotonic conductivity to ferroelasticty happens when there is a change from Phase II to Phase III. The major difference between theses 2 phases is the hydrogen bond arrangement.Paragraph 2Under the opthalmic microscope, we can comment that the polymorphic domains will alter at each phase transmutation to a different extent. We can see in phase III that the domains in the Cs3H(SeO4)2 crystal are made up of polydomains separated by two kinds of domain boundaries. The two kinds of domain boundaries are categorized as the planes of 311 and 11n, where n is decided by the strain compatibility condition. The domains at the sides of each domain boundary are related to the reflective symmetry or the rotational sy mmetry on that boundary itself. Furthermore, we can observe that the angle between any domain and its neighboring domains is approximately cxx, which is very close to the theoretical values calculated using the wicket parameters.As we move on from phase III to phase II, we can observe that the domain structure alters keenly by the phase rebirth of TIIIII. Similarly, the reflective symmetry and rotational symmetry also changes at the akin phase transition. However, the kinds of domain and domain boundary remain the same as those in phase III despite a change in domain pattern. This could be collectible to the slight change in confederation of hydrogen bonding between the SeO4 tetrahedrons when the existing hydrogen bonds were broken to form new weaker  cardinals. This skill explains why their lattice parameters a and b do not really change appreciably. Compared to phase III previously, the angle between any domain and its neighboring domains in phase II is also approximat ely 120 and is justified by the theoretical values determined from the same equation we used for phase III.Hence, this suggest a slight change in the Cs3H(SeO4)2 crystal structure at the phase transition of TIIIII. From phase II to phase I, the domain boundaries is observed to have vaporize just before the curie temperature of the phase transition of TIII and the crystal structure changes from optically biaxial to optically uniaxial. This could be due to an external stress caused by the atomic rearrangement of the SeO4 tetrahedrons in the Cs3H(SeO4)2 crystal as a result of breaking the hydrogen bonds between them.Paragraph 3Higher temperatures for most material will enable atoms to move to low energy locates, fitting into a perfect crystal symmetry. Cs3H(SeO4)2 however behaves differently. As the temperature increases (above 396K), its crystal symmetry decreases when it changes phase from III to II. The orientation of the hydrogen bond for phase II and III differs. For phase I I, the orientation is along 310 and 3-10 direction whereas for phase III, it is parallel to the aaxis. As the transition from phase III to II occurs, the precursor of the superprotonic conductivity is observed. In order for travail of proton to occur, the breaking and thus recombination of hydrogen bonds are required.For phase III, in order for the movement of one proton, the breaking of 2 hydrogen bonds is needed. The reason as to why 2 hydrogen bond is needed to be broken and recombined again is because for the movement of one proton to occur, it must break the hydrogen bond it resides in and and then change its orientation, recombining at other site the mirroring effect of opposite hydrogen bond is required to maintain the crystal symmetry i.e. to say that the another hydrogen bond parallel to the previous hydrogen bond site needs to be broken and recombined at other site parallel to the newly recombined hydrogen bond.In this way, in phase III, the recombination of two hy drogen bonds is simultaneously needed for one proton transport. Phase II however, behaves differently. The movement of the proton is self-governing of the other protons at other hydrogen site. The crystal structure allows for this tractableness of the proton execution, which the superprotonic conduction takes place. The mechanism in which proton transportation occurs in the polymorphs is by the dispersal of protons through a hydrogen bond network, by the cleaving and formation of the hydrogen bonds. However, in certain phases, the cleavage and formation of the hydrogen bond might differ. The fuel cell works on the basis of the movement of protons. The movement of electrons should be disallowed as it would short circuit the fuel cell. Hence, a tissue layer is used to allow only the movement of protons across and not electrons and gases. On top of that, in order for a superprotonic effect to occur, the flexibility for proton motion must be allowed. Hence, the lesser symmetrically patterned the phases the protons reside in, the higher(prenominal) this flexibility.