A silicide hydride is a mixed anion compound that contains silicide (Si4− or clusters) and hydride (H−) anions. The hydrogen is not bound to silicon in these compounds. These can be classed as interstitial hydrides, Hydrogenated zintl phases, or Zintl phase hydrides. In the related silanides, SiH3− anions or groups occur. Where hydrogen is bonded to the silicon, this is a case of anionic hydride, and where it is bonded to a more complex anion, it would be termed polyanionic hydride.
Silicide hydrides may be prepared by heating a Zintl phase or metal silicide under hydrogen pressure, of perhaps 20 atmospheres.
Properties In CaSiD1+x the deuterium atom (D) fits in a tetrahedral hole between three calcium and one silicon atoms. The Si-D distance is 1.82 Å, quite a bit further than then a Si-H covalent bond.
List formulasystemspace groupunit cell ÅvolumedensitycommentreferenceLi4Si2HorthorhombicCmmmzigzag Si chains Si-Si 2.39CaSiHCaSiH1+x x<1.2orthorhombicPnmaa = 14.4884, b = 3.8247, c = 11.2509, Z = 3zigzag Si chains Si-Si 2.47CaAlSiHtrigonalZ=1Al-H bond semimetalCa2SiH2.41amorphousa=5.969 b=3.6146 c=6.815 reversible hydrogen storageCa5Si3H0.53tetrahedralI4/mcma=7.6394 c=14.7935 Z=4863.33SrSiH1.6orthorhombicPnmaSrAlSiHP3m1Al-H bond semimetalSrGaSiHtrigonalP3m1Z=1grey; Ga-H 1.71 semimetalSr21Si2O5H21+xcubicFdma = 19.1190BaSiH3.4orthorhombicPnmaBa3Si4Hx (x = 1–2) tetrahedralI4/mcma ≈ 8.44, c ≈ 11.95, Z = 8Si46– in a butterfly-shapeBa21Si2O5H21+xcubicFdma = 20.336BaAlSiHAl-H bond semimetalBaGaSiHtrigonalP3m1a=4.2934 c=5.186 Z=182.79grey; air stable; Ga-H 1.71 semimetalBaGaSiDtrigonalP3m1a=4.2776 c=5.1948 Z=182.32greyLaFeSiHtetragonalP4/nmma=4.0270 c=8.0374LaFeSiHorthorhombicCmmea=5.6831 b=5.7037 c=7.9728at 15K; superconductor Tc=9.7KLa3Pd5SiD~1.6orthorhombicImmaa=13.193 b=7.638 c=7.916801.8<9.5 barLa3Pd5SiD~2.71orthorhombicImmaa=13.102 b=7.673 c=8.168821.3La3Pd5SiD~5orthorhombicPmnba=13.16 b=7.91 c=8.20854>75 barBaLaSi2D0.80orthorhombicCmcma = 4.6443, b = 15.267, c = 6.7630NdScSiH1.5tetrahedralI4/mmma=4.221 c=16.928 Z=4EuSiH1.8orthorhombicPnmaGdMnSiHtetragonalP4/nmmGdFeSiHtetragonalP4/nmma=3.901 c=7.503114.2GdCoSiHtetragonalP4/nmma=3.879 c=7.439111.9
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