The resulting powder was washed, filtered, and dried overnight at 393 K. The PTFE vessel was put in a Parr digestion apparatus for a hydrothermal synthesis over 10 days at 523 K. A gel was obtained with a pH value around 13. Adequate quantities of sodium silicate solution (27% SiO 2, 8% Na 2O), sodium chloride, hafnium chloride, potassium chloride, sodium hydroxide and water were mixed thoroughly in a polytetrafluoroethylene (PTFE) vessel at room temperature for 30 minutes. H 2O with zirconium totally substituted by hafnium.The first step was the synthesis of the Hf–petarasite phase Na 5Zr 2Si 6O 18(Cl The synthesis of sodium hafnium disilicate was based on the two-step synthesis protocol of parakeldyshite Na 2ZrSi 2O 7 (Lin et al., 1999 Ferreira et al., 2001 ). Since hafnium simulates uranium, the existence of the Na 2USi 2O 7 phase can also be supposed.Ĭell parameters of Na 2ZrSi 2O 7 are from Ferreira et al. This parameter was determined to be 0.018 for a maximum distance between paired atoms of 1 Å, indicating that structures are effectively isostructural. The structures' similarities were estimated by different parameters such as the measure of similarity Δ (Bergerhoff et al., 1999 ). A numerical comparison of the structures of the parakeldyshite and the Na 2HfSi 2O 7 phase was performed with COMPSTRU (de la Flor et al., 2016 ). Since these dimensions are the same in both phases, ion exchange should also be possible in the Na 2HfSi 2O 7 phase. The Na 2ZrSi 2O 7 phase is capable of ion exchange on the sodium site thanks to the sufficient dimension of the sodium tunnels in the direction (Kostov-Kytin et al., 2008 ). A polyhedral view of the Na 2HfSi 2O 7 structure is given in Fig. 1. The sodium coordination polyhedral volumes are quite similar in volume for the two phases, about 30.1 Å 3. It is thus in the latter tetrahedron that the bond lengths differ significantly whereas the other bond lengths are quite similar in both phases. The Si1O 4 tetrahedral volume of the Na 2HfSi 2O 7 phase is about 5% smaller than that in parakeldyshite. For the Na 2HfSi 2O 7 phase, the Hf1O 6 octahedral and the Si2O 4 tetrahedral volumes are about the same as the analogous Zr octahedral and Si tetrahedral volumes in parakeldyshite. As reported in Table 1, the cell parameters of the Na 2HfSi 2O 7 phase are slightly smaller than those of parakeldyshite, and the volume of the cell is 0.8% smaller. NOTE: This does not affect serialization/deserialization via Jason.Encoder when derived.The Na 2HfSi 2O 7 phase is isostructural with the parakeldyshite phase (Voronkov et al., 1970 Fleischer et al., 1979 ). Likewise, the support for defining validation rules inline with usage of field/3, embeds_one/3,Įtc., is strictly additive, and those additions are stripped from the AST before field/3ĭef deps do [ You import it in a scope where you use fstruct/1 already, it will not interfere. Of the functionality provided both by fstruct/1, as well as Ecto.Schema. The functionality provided by the defstruct macro in this module is strictly a superset To define schema'd types in Ecto, can now be used to define structs for general purpose This builds on top of Ecto embedded schemas, so the same familiar syntax you use today Implementing validations, generating changesets from parameters, JSON serialization, Strukt provides an extended defstruct macro which builds on top of Ecto.SchemaĪnd Ecto.Changeset to remove the boilerplate of defining type specifications,
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