[lammps-users] improper_style class2 command

Dear Alex,

I want to simulate a polymer (Polybutylene terephthalate) with class 2 force filed (PCFF). It is a common structure.

I built it in material studio and convert its files (.mdf & .car) to LAMMPS data fie by msi2lmp.

Now, I have problem with the Eaa in the data file. I think the data file is incorrect in this section.

In accordance to User Guide>> Improper Styles >> improper_style class2 command

Teta 1: Teta (ijk), Teta 2: Teta (ijl), Teta3: Teta (kjl)

X 1: dihedral (ijkl) and is the angle between the plane of ijk & jkl (the plane included teta 1 & Teta 3) correspond to M1 (all the thing is OK, X1 & M1 are Brought in the same level).

X 2: dihedral (kjli) and is the angle between the plane of kjl & jli (the plane included teta 3 & Teta 2), this is correspond to M3 (all the thing is correct, but X2 & M3 are Brought in same level which is confusing).

X 3: dihedral (ljik) and is the angle between the plane of lji & jik (the plane included teta 2 & Teta 1), this is correspond to M2 (all the thing is correct, but X3 & M2 are Brought in same level which confusing).

It is the structure of data file which built by msi2lmp

AngleAngle Coeffs

1 0.0000 0.0000 0.0000 117.9400 118.9000 117.9400

2 0.0000 0.0000 0.0000 125.5320 120.7970 108.4400

3 0.0000 0.0000 5.9863 118.9000 116.0640 116.0640

4 0.2738 0.2738 -0.4825 107.6600 110.7700 110.7700

5 0.0000 0.0000 0.0000 107.6600 107.6880 107.6880

6 0.0000 0.0000 0.0000 110.7700 107.4100 107.6880

7 -1.3199 0.1184 -1.3199 110.7700 112.6700 110.7700

8 0.2738 0.2738 -0.4825 107.6600 110.7700 110.7700

9 -0.3157 -0.3157 -0.3157 107.6600 107.6600 107.6600

10 0.2738 0.2738 -0.4825 107.6600 110.7700 110.7700

11 -1.3199 0.1184 -1.3199 110.7700 112.6700 110.7700

I check all the parameters in this section, all rows. The problem is:

The 7th and 11th rows are similar to each other, and in accordance to User Guide it should be as below,

M1 M2 M3 Teta1 Teta2 Teta3

7 0.1184 -1.3199 -1.3199 110.7700 112.6700 110.7700 (In accordance to user guide)

But in data file

7 -1.3199 0.1184 -1.3199 110.7700 112.6700 110.7700 (data file)

M1 should be correspond to the angle between the plane of ijk & jkl (teta 1 & Teta 3),

M2 should be correspond to the angle between the plane of lji & jik (teta 1 & Teta 2),

M3 should be correspond to the angle between the plane of kjl & jli (teta 2 & Teta 3).

In 4th row:

110.7700= Teta 1= c c h

112.6700 = Teta 2= c c c

110.7700= Teta 3= c c h,

M1 should be the dihedral between the planes included Teta 3, 1 (c c h c)= 0.1184 (from PCFF file) but in data file it is -1.3199 and it seems be incorrect.

M2 should be the dihedral between the planes included Teta 1, 2 (c c c h)= -1.3199 (from PCFF file) but in data file it is 0.1184 and it seems be incorrect.

M3 should be the dihedral between the planes included Teta 2, 3(c c c h)= -1.3199 (from PCFF file) and it is correct.

I check all the rows and in these rows the LAMMPS data file is different with User guide, please check it and tell me what I can do.

The MSI files (.car, .mdf ) and data file attach to this email.

I look forward hearing from you.

Sincerely,

maliheh

P1-pcff.car (22.6 KB)

P1-pcff.data (100 KB)

P1-pcff.mdf (24.6 KB)