Standard X-ray Diffraction Powder Patterns

Powder data cards. None.Additional published patterns. None.NBS sample. The sample of lanthanumarsenate was prepared at NBS from a water solution of arsenic pentoxide and lanthanum trichloride. It was dried at 110 °C. Spectrographicanalysis showed the following major impurities:0.01 to 0.1 percent each of aluminum, iron, andsilicon, and 0.001 to 0.01 percent each of calcium, magnesium, lead, and antimony.Lanthanum Arsenate, LaAsO4 (monoclinic)Lattice constantsThe sample was colorless. The indices of refraction could not be determined because thesample was too fine.The rf-values of the three strongest lines are:3.185, 2.983, and 3.391 A.Structural data. No reference to the structureof lanthanum arsenate was found; however, it isapparently isostructural with lanthanum phosphate with the space group Cih-P2i/n (No. 14)and 4(LaAsO4 ) per unit cell.a6cft1963 National Bureau of Standardsat 25 °C.0A7. 0078± . 00070A7. 212±. 0010A6. 7670±. 0007104°29. 3'±. 6'The density of lanthanum arsenate calculated from the NBS lattice constants is 5.572 g/cm3 at 25 °C.hklT01110OilTil101111020200002120210012202212112220122301031103311221122,310013, 131212301231103, 132320023Internal Standard,Silver, a = 4. 0861 ACu, 1.5405 A at 25 °CdA5. 454.954. 854.354. 2153. 6353. 6063. 3913.2783. 1853.0682. 9832.7222. 5462. 5272.4712.4302.3262.2572.2522. 2132. 1852. 1592. 0892. 0231.9911.9591. 9421. 9161.868hklI4 32212 231, 22310 0408132