Ca14Si19 - A Zintl phase with a novel two dimensional silicon framework

Ca14Si19 is an overlooked binary phase in the Ca/Si system with a novel type of twodimensional silicon framework (R(3) over barc$, a = 867.85(6), c = 6852.8(8)pm, Z = 6). The basic building units are 3,3,3-barrelanes Si-11 which are linked by Si bridges to form a twodimensional silicon framework leaving space for interstitial calcium atoms. The thickness of the silicon layers is about 800 pm. The compound is a semiconductor with a band gap of about E(G) = 0.1 eV and a diamagnetic moment of chi(mole) = -9 . 10(-4) cm(3)mol(-1). According to the relatively high linking of silicon atoms the reaction with air and moisture is fairly slow.