The electronic structures of the tetragonal and hexagonal Zn

2

SiO

4

with super cells of 28 and 126 atoms were calculated by Vienna ab-initio Simulation Package with ultrasoft pseudopotentials.The calculated equilibrium lattice constants agree much well with the experimental values.Using the optimized equilibrium lattice constants

the densities of states and energy band structures were further calculated.The total densities of states of both structures show the valence and conduction bands.By analyzing the partial densities of states

the contributions of different electron states in different atoms are estimated.The d states of Zn and p states of Omostly contribute to the top of the valence band

and the s states of Zn make major effects on the bottom of conduction band.The similar densities of states in the mass of the two structures suggest that both structures have the similar electronic and optical properties.Moreover

the calculated energy band structures show that the tetragonal and hexagonal Zn

2

SiO

4

have direct energy band gaps

which are promising semiconductors for short wavelength optoelectronic devices.