.n2t File

To translate atom names into atom types, the x2top program uses library files called .n2t files as input. These files contain information about atom types, charges, and connectivity to neighbors. The format of such a file is exemplified by:

C    opls_157    -0.18  12.011  4    H 0.108   H 0.108   H 0.108   C 0.150

The above line interprets an atom named C to be the carbon atom in CH3, CH2, or alcohols (atom type opls_157). This atom is assigned a charge of -0.18 and has a mass of 12.011 (standard carbon mass). The number 4 indicates that this carbon atom is bonded to four other atoms, given in the subsequent entries on the same line. This particular entry indicates that this carbon atom is bonded to three hydrogens, each at a distance of 0.108 nm, and another carbon atom at a distance of 0.150 nm.