       10
surface structure 
O            1.27982456        0.00000000        6.26955000
Si           2.08985000        1.33345000        5.45952414
O            2.89987632        0.00000000        4.64949828
O            0.81002632        1.33345000        4.17970000
Si           0.00000000        0.00000000        3.36967414
O            3.36967460        1.33345000        2.55964828
O            1.27982460        0.00000000        2.08985000
Si           2.08985000        1.33345000        1.27982414
O            2.89987636        0.00000000        0.46979828
O            0.81002636        1.33345000        0.00000000
