Compare and contrast the crystal structures and crystal chemistry of quartz, α-FePO4 and β-FePO4.
FePO4 is also known as Iron (III) phosphate. Iron (III) phosphate is an inorganic compound. Most of the FeP04 has the structure of α-quartz which is α-FePO4. It has a tetrahedral molecular geometry. α-FePO4 is present at pretty low degree Celsius. It is also a transition metal as it is in the d-block in the periodic table. It can be studied at many different temperature which range from 294K to 1073K with the use of neutron powder diffraction. When there is an increase in pressure, it will lead to a phase change. This causes the octahedral Fe centres to become denser. It will thus lead to the formation of β-FePO4. This transition of α-FePO4 to β-FePO4 occurs at about 980K which is about 706 degree Celcius. The transition will result in irregularity in the structure. Firstly, let’s look at α- FePO4. When there is an increase in heat, it will result in a non-linear increase in the boundary and in turn cause the volume of α-FePO4 to increase. α-FePO4 has a thermal expansion coefficient of α (K-1)= 2.924 x 10-5 + 2.920 x 10-10 ( T-300)2 as stated in the study that we were supposed to refer to. α-FePO4 is very unique as the rotation frequency of α-FePO4 is very close to a natural internal vibration frequency. Secondly, let’s look at β-FePO4 to compare the difference in their crystal structures and crystal chemistry of the quarts. With reference to the study, it states that the α-β transition can be represented using a single order parameter known as the tilt angle. The tilt angle depends on the fractional atomic coordinates of oxygen atoms. The degree of tilt angle will affect the temperature using this expression: δ2 = 2/3 δ0^2 [1 + (1 – ¾ (T – Tc/T0 – Tc))^1/2] which can also be found from the study. At 980K, the tilt angle will decrease and it can be represented by symbol δ0 as seen in the equation above. The symbol Tc which is also in the above equation represents the temperature for the second-order transition. Illustrate and describe the symmetrical differences between α-FePO4 and β-FePO4 As mentioned in the paragraph one above, α- β transition will takes place about 980k. Both α-FePO4 and β-FePO4 are similar in the sense that both of them a formula unit in its unit cell. Likewise, both α-FePO4 and β-FePO4 also have the same extent of symmetry. However, the difference between α- FePO4 and β-FePO4 is that α- FePO4 has a trigonal unit cell while on the other hand, β- FePO4 has a hexagonal unit cell. With reference to the Table showing the lattice parameters’ correspondence with temperature as seen in the study, when temperature increases but it is still at a temperature which is less than 980K, the cell boundary will increase which will in turn lead to an increase in volume. The Fe-O-P bond expands and increase significantly at the same time. As the temperature approaches towards 980K, α- β transition will occur. For β- FePO4 which is unlike α- FePO4, the bond distance and tilt angle will not change much with the …show more content…
The tilt angle continues to decrease when the temperature increases. This shows that they have a negative correlation.
Describe changes in the FeO4 and PO4 tetrahedral with temperature and explain tetrahedral tilting quantitatively. When α - β transition takes place at 980K, the structural integrity and properties depends significantly on the PO4 tetrahedrons. The tilt angle is one of the significant factor which will lead to tetrahedral distortion. Tetrahedral distortion occurs when there is a change in the angle and also the change in the length of the bonds. The tilt angle as mentioned in paragraph 2 above, is inversely correlated with temperature. Another factor which led to tetrahedral distortion is due to the change in bond length and the change in O-PO angle which defers according to temperature. This means that when the temperature reaches roughly about 980K, the Fe—O—P bridging angles will increase and the tilt angles will decrease strongly. For the quartz-type FePO4, the bond distance and volume of the phase increases significantly and non-linearly as a function of temperature. The temperature dependence of this tilt angle can be reflected using Landau-type model expressed as
FePO4 is also known as Iron (III) phosphate. Iron (III) phosphate is an inorganic compound. Most of the FeP04 has the structure of α-quartz which is α-FePO4. It has a tetrahedral molecular geometry. α-FePO4 is present at pretty low degree Celsius. It is also a transition metal as it is in the d-block in the periodic table. It can be studied at many different temperature which range from 294K to 1073K with the use of neutron powder diffraction. When there is an increase in pressure, it will lead to a phase change. This causes the octahedral Fe centres to become denser. It will thus lead to the formation of β-FePO4. This transition of α-FePO4 to β-FePO4 occurs at about 980K which is about 706 degree Celcius. The transition will result in irregularity in the structure. Firstly, let’s look at α- FePO4. When there is an increase in heat, it will result in a non-linear increase in the boundary and in turn cause the volume of α-FePO4 to increase. α-FePO4 has a thermal expansion coefficient of α (K-1)= 2.924 x 10-5 + 2.920 x 10-10 ( T-300)2 as stated in the study that we were supposed to refer to. α-FePO4 is very unique as the rotation frequency of α-FePO4 is very close to a natural internal vibration frequency. Secondly, let’s look at β-FePO4 to compare the difference in their crystal structures and crystal chemistry of the quarts. With reference to the study, it states that the α-β transition can be represented using a single order parameter known as the tilt angle. The tilt angle depends on the fractional atomic coordinates of oxygen atoms. The degree of tilt angle will affect the temperature using this expression: δ2 = 2/3 δ0^2 [1 + (1 – ¾ (T – Tc/T0 – Tc))^1/2] which can also be found from the study. At 980K, the tilt angle will decrease and it can be represented by symbol δ0 as seen in the equation above. The symbol Tc which is also in the above equation represents the temperature for the second-order transition. Illustrate and describe the symmetrical differences between α-FePO4 and β-FePO4 As mentioned in the paragraph one above, α- β transition will takes place about 980k. Both α-FePO4 and β-FePO4 are similar in the sense that both of them a formula unit in its unit cell. Likewise, both α-FePO4 and β-FePO4 also have the same extent of symmetry. However, the difference between α- FePO4 and β-FePO4 is that α- FePO4 has a trigonal unit cell while on the other hand, β- FePO4 has a hexagonal unit cell. With reference to the Table showing the lattice parameters’ correspondence with temperature as seen in the study, when temperature increases but it is still at a temperature which is less than 980K, the cell boundary will increase which will in turn lead to an increase in volume. The Fe-O-P bond expands and increase significantly at the same time. As the temperature approaches towards 980K, α- β transition will occur. For β- FePO4 which is unlike α- FePO4, the bond distance and tilt angle will not change much with the …show more content…
The tilt angle continues to decrease when the temperature increases. This shows that they have a negative correlation.
Describe changes in the FeO4 and PO4 tetrahedral with temperature and explain tetrahedral tilting quantitatively. When α - β transition takes place at 980K, the structural integrity and properties depends significantly on the PO4 tetrahedrons. The tilt angle is one of the significant factor which will lead to tetrahedral distortion. Tetrahedral distortion occurs when there is a change in the angle and also the change in the length of the bonds. The tilt angle as mentioned in paragraph 2 above, is inversely correlated with temperature. Another factor which led to tetrahedral distortion is due to the change in bond length and the change in O-PO angle which defers according to temperature. This means that when the temperature reaches roughly about 980K, the Fe—O—P bridging angles will increase and the tilt angles will decrease strongly. For the quartz-type FePO4, the bond distance and volume of the phase increases significantly and non-linearly as a function of temperature. The temperature dependence of this tilt angle can be reflected using Landau-type model expressed as