The material structure described by Na2Mn2Si2O7 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 5-coordinate geometry to one O(1), one O(3), one O(4), one O(5), and one O(7) atom. In the second Na site, Na(2) is bonded in a distorted see-saw-like geometry to one O(3), one O(4), one O(6), and one O(7) atom. There are two inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to one O(2), one O(3), one O(6), and one O(7) atom to form MnO4 tetrahedra that share corners with two equivalent Si(1)O4 tetrahedra and corners with two equivalent Si(2)O4 tetrahedra. In the second Mn site, Mn(2) is bonded in a 6-coordinate geometry to one O(1), one O(4), one O(5), one O(6), and two equivalent O(2) atoms. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(2), one O(4), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(2)O4 tetrahedra and corners with two equivalent Mn(1)O4 tetrahedra. In the second Si site, Si(2) is bonded to one O(1), one O(3), one O(5), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra and corners with two equivalent Mn(1)O4 tetrahedra. There are seven inequivalent O sites. In the first O site, O(3) is bonded to one Na(1), one Na(2), one Mn(1), and one Si(2) atom to form corner-sharing ONa2MnSi tetrahedra. In the second O site, O(4) is bonded in a 4-coordinate geometry to one Na(1), one Na(2), one Mn(2), and one Si(1) atom. In the third O site, O(5) is bonded in a distorted trigonal planar geometry to one Na(1), one Mn(2), and one Si(2) atom. In the fourth O site, O(6) is bonded to one Na(2), one Mn(1), one Mn(2), and one Si(1) atom to form distorted corner-sharing ONaMn2Si tetrahedra. In the fifth O site, O(7) is bonded in a 4-coordinate geometry to one Na(1), one Na(2), one Mn(1), and one Si(2) atom. In the sixth O site, O(1) is bonded in a distorted bent 120 degrees geometry to one Na(1), one Mn(2), one Si(1), and one Si(2) atom. In the seventh O site, O(2) is bonded in a 4-coordinate geometry to one Mn(1), two equivalent Mn(2), and one Si(1) atom. is represented by the CIF file [CIF]
data_Na2Mn2Si2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   13.478
_cell_length_b   5.822
_cell_length_c   10.628
_cell_angle_alpha   56.703
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   697.027
_cell_formula_units_Z   4
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
loop_
 _atom_site_type_symbol
 _atom_site_label
 _atom_site_symmetry_multiplicity
 _atom_site_fract_x
 _atom_site_fract_y
 _atom_site_fract_z
 _atom_site_occupancy
  Na  Na0  1  0.753  0.589  0.695  1.0
  Na  Na1  1  0.253  0.411  0.805  1.0
  Na  Na2  1  0.247  0.411  0.305  1.0
  Na  Na3  1  0.747  0.589  0.195  1.0
  Na  Na4  1  0.840  0.948  0.384  1.0
  Na  Na5  1  0.340  0.052  0.116  1.0
  Na  Na6  1  0.160  0.052  0.616  1.0
  Na  Na7  1  0.660  0.948  0.884  1.0
  Mn  Mn8  1  0.993  0.571  0.291  1.0
  Mn  Mn9  1  0.493  0.429  0.209  1.0
  Mn  Mn10  1  0.007  0.429  0.709  1.0
  Mn  Mn11  1  0.507  0.571  0.791  1.0
  Mn  Mn12  1  0.919  0.780  0.883  1.0
  Mn  Mn13  1  0.419  0.220  0.617  1.0
  Mn  Mn14  1  0.081  0.220  0.117  1.0
  Mn  Mn15  1  0.581  0.780  0.383  1.0
  Si  Si16  1  0.119  0.848  0.972  1.0
  Si  Si17  1  0.619  0.152  0.528  1.0
  Si  Si18  1  0.881  0.152  0.028  1.0
  Si  Si19  1  0.381  0.848  0.472  1.0
  Si  Si20  1  0.833  0.266  0.550  1.0
  Si  Si21  1  0.333  0.734  0.950  1.0
  Si  Si22  1  0.167  0.734  0.450  1.0
  Si  Si23  1  0.667  0.266  0.050  1.0
  O  O24  1  0.790  0.335  0.042  1.0
  O  O25  1  0.290  0.665  0.458  1.0
  O  O26  1  0.210  0.665  0.958  1.0
  O  O27  1  0.710  0.335  0.542  1.0
  O  O28  1  0.959  0.394  0.908  1.0
  O  O29  1  0.459  0.606  0.592  1.0
  O  O30  1  0.041  0.606  0.092  1.0
  O  O31  1  0.541  0.394  0.408  1.0
  O  O32  1  0.867  0.340  0.382  1.0
  O  O33  1  0.367  0.660  0.118  1.0
  O  O34  1  0.133  0.660  0.618  1.0
  O  O35  1  0.633  0.340  0.882  1.0
  O  O36  1  0.836  0.957  0.977  1.0
  O  O37  1  0.336  0.043  0.523  1.0
  O  O38  1  0.164  0.043  0.023  1.0
  O  O39  1  0.664  0.957  0.477  1.0
  O  O40  1  0.848  0.943  0.680  1.0
  O  O41  1  0.348  0.057  0.820  1.0
  O  O42  1  0.152  0.057  0.320  1.0
  O  O43  1  0.652  0.943  0.180  1.0
  O  O44  1  0.940  0.981  0.191  1.0
  O  O45  1  0.440  0.019  0.309  1.0
  O  O46  1  0.060  0.019  0.809  1.0
  O  O47  1  0.560  0.981  0.691  1.0
  O  O48  1  0.883  0.485  0.583  1.0
  O  O49  1  0.383  0.515  0.917  1.0
  O  O50  1  0.117  0.515  0.417  1.0
  O  O51  1  0.617  0.485  0.083  1.0
[/CIF]
.
The material structure described by Na2Mn2Si2O7 crystallizes in the monoclinic P2_1/c space group. There are two inequivalent Na sites. In the first Na site, Na(1) is bonded in a 5-coordinate geometry to one O(1), one O(3), one O(4), one O(5), and one O(7) atom. In the second Na site, Na(2) is bonded in a distorted see-saw-like geometry to one O(3), one O(4), one O(6), and one O(7) atom. There are two inequivalent Mn sites. In the first Mn site, Mn(1) is bonded to one O(2), one O(3), one O(6), and one O(7) atom to form MnO4 tetrahedra that share corners with two equivalent Si(1)O4 tetrahedra and corners with two equivalent Si(2)O4 tetrahedra. In the second Mn site, Mn(2) is bonded in a 6-coordinate geometry to one O(1), one O(4), one O(5), one O(6), and two equivalent O(2) atoms. There are two inequivalent Si sites. In the first Si site, Si(1) is bonded to one O(1), one O(2), one O(4), and one O(6) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(2)O4 tetrahedra and corners with two equivalent Mn(1)O4 tetrahedra. In the second Si site, Si(2) is bonded to one O(1), one O(3), one O(5), and one O(7) atom to form SiO4 tetrahedra that share  a cornercorner with one Si(1)O4 tetrahedra and corners with two equivalent Mn(1)O4 tetrahedra. There are seven inequivalent O sites. In the first O site, O(3) is bonded to one Na(1), one Na(2), one Mn(1), and one Si(2) atom to form corner-sharing ONa2MnSi tetrahedra. In the second O site, O(4) is bonded in a 4-coordinate geometry to one Na(1), one Na(2), one Mn(2), and one Si(1) atom. In the third O site, O(5) is bonded in a distorted trigonal planar geometry to one Na(1), one Mn(2), and one Si(2) atom. In the fourth O site, O(6) is bonded to one Na(2), one Mn(1), one Mn(2), and one Si(1) atom to form distorted corner-sharing ONaMn2Si tetrahedra. In the fifth O site, O(7) is bonded in a 4-coordinate geometry to one Na(1), one Na(2), one Mn(1), and one Si(2) atom. In the sixth O site, O(1) is bonded in a distorted bent 120 degrees geometry to one Na(1), one Mn(2), one Si(1), and one Si(2) atom. In the seventh O site, O(2) is bonded in a 4-coordinate geometry to one Mn(1), two equivalent Mn(2), and one Si(1) atom. is represented by the CIF file [CIF]
data_Na2Mn2Si2O7
_symmetry_space_group_name_H-M   'P 1'
_cell_length_a   13.478
_cell_length_b   5.822
_cell_length_c   10.628
_cell_angle_alpha   56.703
_cell_angle_beta   90.000
_cell_angle_gamma   90.000
_symmetry_Int_Tables_number   1
_cell_volume   697.027
_cell_formula_units_Z   4
loop_
 _symmetry_equiv_pos_site_id
 _symmetry_equiv_pos_as_xyz
  1  'x, y, z'
loop_
 _atom_site_type_symbol
 _atom_site_label
 _atom_site_symmetry_multiplicity
 _atom_site_fract_x
 _atom_site_fract_y
 _atom_site_fract_z
 _atom_site_occupancy
  Na  Na0  1  0.753  0.589  0.695  1.0
  Na  Na1  1  0.253  0.411  0.805  1.0
  Na  Na2  1  0.247  0.411  0.305  1.0
  Na  Na3  1  0.747  0.589  0.195  1.0
  Na  Na4  1  0.840  0.948  0.384  1.0
  Na  Na5  1  0.340  0.052  0.116  1.0
  Na  Na6  1  0.160  0.052  0.616  1.0
  Na  Na7  1  0.660  0.948  0.884  1.0
  Mn  Mn8  1  0.993  0.571  0.291  1.0
  Mn  Mn9  1  0.493  0.429  0.209  1.0
  Mn  Mn10  1  0.007  0.429  0.709  1.0
  Mn  Mn11  1  0.507  0.571  0.791  1.0
  Mn  Mn12  1  0.919  0.780  0.883  1.0
  Mn  Mn13  1  0.419  0.220  0.617  1.0
  Mn  Mn14  1  0.081  0.220  0.117  1.0
  Mn  Mn15  1  0.581  0.780  0.383  1.0
  Si  Si16  1  0.119  0.848  0.972  1.0
  Si  Si17  1  0.619  0.152  0.528  1.0
  Si  Si18  1  0.881  0.152  0.028  1.0
  Si  Si19  1  0.381  0.848  0.472  1.0
  Si  Si20  1  0.833  0.266  0.550  1.0
  Si  Si21  1  0.333  0.734  0.950  1.0
  Si  Si22  1  0.167  0.734  0.450  1.0
  Si  Si23  1  0.667  0.266  0.050  1.0
  O  O24  1  0.790  0.335  0.042  1.0
  O  O25  1  0.290  0.665  0.458  1.0
  O  O26  1  0.210  0.665  0.958  1.0
  O  O27  1  0.710  0.335  0.542  1.0
  O  O28  1  0.959  0.394  0.908  1.0
  O  O29  1  0.459  0.606  0.592  1.0
  O  O30  1  0.041  0.606  0.092  1.0
  O  O31  1  0.541  0.394  0.408  1.0
  O  O32  1  0.867  0.340  0.382  1.0
  O  O33  1  0.367  0.660  0.118  1.0
  O  O34  1  0.133  0.660  0.618  1.0
  O  O35  1  0.633  0.340  0.882  1.0
  O  O36  1  0.836  0.957  0.977  1.0
  O  O37  1  0.336  0.043  0.523  1.0
  O  O38  1  0.164  0.043  0.023  1.0
  O  O39  1  0.664  0.957  0.477  1.0
  O  O40  1  0.848  0.943  0.680  1.0
  O  O41  1  0.348  0.057  0.820  1.0
  O  O42  1  0.152  0.057  0.320  1.0
  O  O43  1  0.652  0.943  0.180  1.0
  O  O44  1  0.940  0.981  0.191  1.0
  O  O45  1  0.440  0.019  0.309  1.0
  O  O46  1  0.060  0.019  0.809  1.0
  O  O47  1  0.560  0.981  0.691  1.0
  O  O48  1  0.883  0.485  0.583  1.0
  O  O49  1  0.383  0.515  0.917  1.0
  O  O50  1  0.117  0.515  0.417  1.0
  O  O51  1  0.617  0.485  0.083  1.0
[/CIF]
.