一、notes：
1、不在data文件裏寫“#”（註釋），否則，容易出錯；
2、前兩行不用寫東西（建議）；
3、相互作用係數可以不用寫在data裏邊（如pair_coeff等），可有可無，but for pair_coeff，最好還是在data文件中設定，因爲它比在in文件中設定更加方便、簡潔。
二、主體框架（必須要有）：
1.數目：原子、鍵、角、二面角、非二面角的的總數目
2.類型：原子、鍵、角、二面角、非二面角
3.box的大小：x、y、z
4.masses（質量）
5.Atoms
6.Bonds
7.Angles
8....
三、example（轉載：http://blog.sina.com.cn/s/blog_b48a7ac30102w4pr.html）
Here is a sample file with annotations in parenthesis and lengthy sections replaced by dots (...). Note that the blank lines are important in this example.
LAMMPS Description (1st line of file) 100 atoms (this must be the 3rd line, 1st 2 lines are ignored) 95 bonds (# of bonds to be simulated) 50 angles (include these lines even if number = 0) 30 dihedrals 20 impropers 5 atom types (# of nonbond atom types) 10 bond types (# of bond types = sets of bond coefficients) 18 angle types 20 dihedral types (do not include a bond,angle,dihedral,improper type 2 improper types line if number of bonds,angles,etc is 0) -0.5 0.5 xlo xhi (for periodic systems this is box size, -0.5 0.5 ylo yhi for non-periodic it is min/max extent of atoms) -0.5 0.5 zlo zhi (do not include this line for 2-d simulations) Masses 1 mass ... N mass (N = # of atom types) Nonbond Coeffs 1 coeff1 coeff2 ... ... N coeff1 coeff2 ... (N = # of atom types) Bond Coeffs 1 coeff1 coeff2 ... ... N coeff1 coeff2 ... (N = # of bond types) Angle Coeffs 1 coeff1 coeff2 ... ... N coeff1 coeff2 ... (N = # of angle types) Dihedral Coeffs 1 coeff1 coeff2 ... ... N coeff1 coeff2 ... (N = # of dihedral types) Improper Coeffs 1 coeff1 coeff2 ... ... N coeff1 coeff2 ... (N = # of improper types) BondBond Coeffs 1 coeff1 coeff2 ... ... N coeff1 coeff2 ... (N = # of angle types) BondAngle Coeffs 1 coeff1 coeff2 ... ... N coeff1 coeff2 ... (N = # of angle types) MiddleBondTorsion Coeffs 1 coeff1 coeff2 ... ... N coeff1 coeff2 ... (N = # of dihedral types) EndBondTorsion Coeffs 1 coeff1 coeff2 ... ... N coeff1 coeff2 ... (N = # of dihedral types) AngleTorsion Coeffs 1 coeff1 coeff2 ... ... N coeff1 coeff2 ... (N = # of dihedral types) AngleAngleTorsion Coeffs 1 coeff1 coeff2 ... ... N coeff1 coeff2 ... (N = # of dihedral types) BondBond13 Coeffs 1 coeff1 coeff2 ... ... N coeff1 coeff2 ... (N = # of dihedral types) AngleAngle Coeffs 1 coeff1 coeff2 ... ... N coeff1 coeff2 ... (N = # of improper types) Atoms 1 molecule-tag atom-type q x y z nx ny nz (nx,ny,nz are optional - ... see "true flag" input command) ... N molecule-tag atom-type q x y z nx ny nz (N = # of atoms) Velocities 1 vx vy vz ... ... N vx vy vz (N = # of atoms) Bonds 1 bond-type atom-1 atom-2 ... N bond-type atom-1 atom-2 (N = # of bonds) Angles 1 angle-type atom-1 atom-2 atom-3 (atom-2 is the center atom in angle) ... N angle-type atom-1 atom-2 atom-3 (N = # of angles) Dihedrals 1 dihedral-type atom-1 atom-2 atom-3 atom-4 (atoms 2-3 form central bond) ... N dihedral-type atom-1 atom-2 atom-3 atom-4 (N = # of dihedrals) Impropers 1 improper-type atom-1 atom-2 atom-3 atom-4 (atom-2 is central atom) ... N improper-type atom-1 atom-2 atom-3 atom-4 (N = # of impropers)
注意：data文件不僅能夠表示座標，鍵，鍵角等，而且可以輸入初始速度，鍵係數等信息。
原文出處：https://www.cnblogs.com/sysu/p/10808688.html