top.txt

<atomTypes>
1 X
2 X
3 X
4 X
<end>

<masses>
1 1.0
2 1.0
3 1.0
4 1.0
<end>

<bonds>
1 2 1.1 10
2 3 1.1 10
3 4 1.1 10
<end>

<angles>
1 2 3 120 1
2 3 4 90 1
<end>

<dihedrals>
1 2 3 4 90 5
<end>

<charges>
1 1.0
2 0.0
3 0.0
4 -1.0
<end>

<vdw>
1 3 1.0 1.0
2 4 1.0 1.0
1 4 1.0 1.0
<end>

<box>
1000.0 1000.0 1000.0
<end>