| dc.description.abstract | Optical coatings are thin layers of materials applied to optical components in order to modify the transmission, reflection, or polarization properties of light. The common materials used for optical coatings include magnesium fluoride (MgF2
), scandium trifluoride (ScF3
), and aluminum trifluoride (AlF3
), owing to their desirable optical properties, spectral range, and compatibility with substrates. However, each of these materials has its own drawbacks. For instance, AlF3
has been found to exhibit limited resistance to attack by chemicals, as well as poor thermal stability, while MgF2
has low durability, as well as being hygroscopic. In this study, we undertook ab initio calculations in order to compare the thermal properties of AlF3
, ScF3
, Al0.5Sc0.5F3
, and In0.5Sc0.5F3
in order to obtain the best material for optical coatings. MgF2
was also included in the study as a reference. The calculations used PBE pseudopotentials and the extended generalized gradient approximation within the quantum espresso algorithm. The study demonstrated that the computed results agree with the information found in the literature. ScF3
exhibited a negative coefficient of thermal expansion, unlike the other four. Moreover, AlF3
was found to be the best candidate for optical coatings that are used in high-power laser systems with high thermal dissipation, due to its superior thermal expansion coefficient as well as its better response to thermal stress. The large variation between the cp
and cv
of ScF3
is not desirable. Moreover, due to its negative thermal expansion coefficient, ScF3
is not thermally stable. The highest thermal stability was exhibited by In0.5Sc0.5F3
. Since Al0.5Sc0.5F3
and In0.5Sc0.5F3
have been modeled in this study for the first time, experimental determination of their crystal structures needs to be investigated. | en_US |
