convergence in electric field

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convergence in electric field
Date: 2023/01/29 02:01 Name: maedeh <mashhadbani.m@gmail.com> hi everyone i apply an external electric field perpendicular to a nanoribbon and I used : scf.Electric.Field 0.0 0.0 0.5*10^(-19) # default=0.0 0.0 0.0 (GV/m) at the first step, I try to relax my system but it doesn't converge. The strength of the electric field is 0.5V/A˚ do i have to modify something else?

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Re: convergence in electric field ( No.1 )

Date: 2023/01/30 20:48
Name: Yung-Ting Lee

Dear maedeh,

(1) 0.5 V/angstrom = 0.5 *10^(-9) GV/angstrom = 0.5 *10^(-9+10) GV/m = 5.0 (GV/m).

For applying an external electric field perpendicular to a nanoribbon, one may set a command line as below.

scf.Electric.Field 0.0 0.0 5.0 # applying an external electric field in the z-axis (unit=GV/m)

(2) The relaxation may not converge at less than 100 steps because electron density will be slightly changed due to an applied electric field.

The number of relaxation steps could be larger than 100 to reach energy and force convergences.

One may restart the relaxations or increase the number of steps to find the optimization structure with an applied electric field.

On the other hand, sometimes, atoms will be driven to move due to a change in electron density by an external electric field.

Therefore, fixing several atoms may be necessary in order to help the structure reach convergence easily. Otherwise, atoms move all the time in the unit cell.

Best regards,
Yung-Ting Lee

Re: convergence in electric field ( No.2 )

Date: 2023/02/06 14:26
Name: maedeh <mashhadbani.m@gmail.com>

i did what you say and also I decrease the electric field strength but the system didn't converge the system after 119 step is:
https://s2.uupload.ir/files/untitled_dk9n.png

Re: convergence in electric field ( No.3 )

Date: 2023/02/06 14:34
Name: maedeh <mashhadbani.m@gmail.com>

this is my *.dat file:

scf.Electric.Field 0.0 0.2 0.0 # default=0.0 0.0 0.0 (GV/m)

Atoms.Number 72
Atoms.SpeciesAndCoordinates.Unit FRAC
<Atoms.SpeciesAndCoordinates
1 Sn 0.0000000 0.0973830 0.0000000 7.0 7.0
2 Sn 0.0555560 0.0389700 0.0560000 7.0 7.0
3 Sn 0.1666670 0.0389700 0.0000000 7.0 7.0
4 Sn 0.2222220 0.0973830 0.0560000 7.0 7.0
5 Sn 0.3333330 0.0973830 0.0000000 7.0 7.0
6 Sn 0.3888890 0.0389700 0.0560000 7.0 7.0
7 Sn 0.5000000 0.0389700 0.0000000 7.0 7.0
8 Sn 0.5555560 0.0973830 0.0560000 7.0 7.0
9 Sn 0.6666670 0.0973830 0.0000000 7.0 7.0
10 Sn 0.7222220 0.0389700 0.0560000 7.0 7.0
11 Sn 0.8333330 0.0389700 0.0000000 7.0 7.0
12 Sn 0.8888890 0.0973830 0.0560000 7.0 7.0
13 Sn 0.0000000 0.2142080 0.0000000 7.0 7.0
14 Sn 0.0555560 0.1557950 0.0560000 7.0 7.0
15 Sn 0.1666670 0.1557950 0.0000000 7.0 7.0
16 Sn 0.2222220 0.2142080 0.0560000 7.0 7.0
17 Sn 0.3333330 0.2142080 0.0000000 7.0 7.0
18 Sn 0.3888890 0.1557950 0.0560000 7.0 7.0
19 Sn 0.5000000 0.1557950 0.0000000 7.0 7.0
20 Sn 0.5555560 0.2142080 0.0560000 7.0 7.0
21 Sn 0.6666670 0.2142080 0.0000000 7.0 7.0
22 Sn 0.7222220 0.1557950 0.0560000 7.0 7.0
23 Sn 0.8333330 0.1557950 0.0000000 7.0 7.0
24 Sn 0.8888890 0.2142080 0.0560000 7.0 7.0
25 Sn 0.0000000 0.3310330 0.0000000 7.0 7.0
26 Sn 0.0555560 0.2726200 0.0560000 7.0 7.0
27 Sn 0.1666670 0.2726200 0.0000000 7.0 7.0
28 Sn 0.2222220 0.3310330 0.0560000 7.0 7.0
29 Sn 0.3333330 0.3310330 0.0000000 7.0 7.0
30 Sn 0.3888890 0.2726200 0.0560000 7.0 7.0
31 Sn 0.5000000 0.2726200 0.0000000 7.0 7.0
32 Sn 0.5555560 0.3310330 0.0560000 7.0 7.0
33 Sn 0.6666670 0.3310330 0.0000000 7.0 7.0
34 Sn 0.7222220 0.2726200 0.0560000 7.0 7.0
35 Sn 0.8333330 0.2726200 0.0000000 7.0 7.0
36 Sn 0.8888890 0.3310330 0.0560000 7.0 7.0
37 Sn 0.0000000 0.4478580 0.0000000 7.0 7.0
38 Sn 0.0555560 0.3894450 0.0560000 7.0 7.0
39 Sn 0.1666670 0.3894450 0.0000000 7.0 7.0
40 Sn 0.2222220 0.4478580 0.0560000 7.0 7.0
41 Sn 0.3333330 0.4478580 0.0000000 7.0 7.0
42 Sn 0.3888890 0.3894450 0.0560000 7.0 7.0
43 Sn 0.5000000 0.3894450 0.0000000 7.0 7.0
44 Sn 0.5555560 0.4478580 0.0560000 7.0 7.0
45 Sn 0.6666670 0.4478580 0.0000000 7.0 7.0
46 Sn 0.7222220 0.3894450 0.0560000 7.0 7.0
47 Sn 0.8333330 0.3894450 0.0000000 7.0 7.0
48 Sn 0.8888890 0.4478580 0.0560000 7.0 7.0
49 Sn 0.0000000 0.5646830 0.0000000 7.0 7.0
50 Sn 0.0555560 0.5062700 0.0560000 7.0 7.0
51 Sn 0.1666670 0.5062700 0.0000000 7.0 7.0
52 Sn 0.2222220 0.5646830 0.0560000 7.0 7.0
53 Sn 0.3333330 0.5646830 0.0000000 7.0 7.0
54 Sn 0.3888890 0.5062700 0.0560000 7.0 7.0
55 Sn 0.5000000 0.5062700 0.0000000 7.0 7.0
56 Sn 0.5555560 0.5646830 0.0560000 7.0 7.0
57 Sn 0.6666670 0.5646830 0.0000000 7.0 7.0
58 Sn 0.7222220 0.5062700 0.0560000 7.0 7.0
59 Sn 0.8333330 0.5062700 0.0000000 7.0 7.0
60 Sn 0.8888890 0.5646830 0.0560000 7.0 7.0
61 H 0.0370640 0.6036530 0.0000000 0.5 0.5
62 H 0.0184910 0.0000000 0.0560000 0.5 0.5
63 H 0.2037310 0.0000000 0.0000000 0.5 0.5
64 H 0.1851580 0.6036530 0.0560000 0.5 0.5
65 H 0.3703980 0.6036530 0.0000000 0.5 0.5
66 H 0.3518240 0.0000000 0.0560000 0.5 0.5
67 H 0.5370640 0.0000000 0.0000000 0.5 0.5
68 H 0.5184910 0.6036530 0.0560000 0.5 0.5
69 H 0.7037310 0.6036530 0.0000000 0.5 0.5
70 H 0.6851580 0.0000000 0.0560000 0.5 0.5
71 H 0.8703980 0.0000000 0.0000000 0.5 0.5
72 H 0.8518240 0.6036530 0.0560000 0.5 0.5
Atoms.SpeciesAndCoordinates>

Atoms.UnitVectors.Unit Ang
<Atoms.UnitVectors
24.2820000 0.0000000 0.0000000
0.0000000 40.0000000 0.0000000
0.0000000 0.0000000 15.0000000
Atoms.UnitVectors>

<MD.Fixed.XYZ
1 1 1 1
2 1 1 1
3 1 1 1
4 1 1 1
5 1 1 1
6 1 1 1
7 1 1 1
8 1 1 1
9 1 1 1
10 1 1 1
11 1 1 1
12 1 1 1
13 1 1 1
14 1 1 1
15 1 1 1
16 1 1 1
17 1 1 1
18 1 1 1
19 1 1 1
20 1 1 1
21 1 1 1
22 1 1 1
23 1 1 1
24 1 1 1
25 1 1 1
26 1 1 1
27 1 1 1
28 1 1 1
29 1 1 1
30 1 1 1
31 1 1 1
32 1 1 1
33 1 1 1
34 1 1 1
35 1 1 1
36 1 1 1
37 1 1 1
38 1 1 1
39 1 1 1
40 1 1 1
41 1 1 1
42 1 1 1
43 1 1 1
44 1 1 1
45 1 1 1
46 1 1 1
47 1 1 1
48 1 1 1
49 1 1 1
50 1 1 1
51 1 1 1
52 1 1 1
53 1 1 1
54 1 1 1
55 1 1 1
56 1 1 1
57 1 1 1
58 1 1 1
59 1 1 1
60 1 1 1
61 1 1 1
62 1 1 1
63 1 1 1
64 1 1 1
65 1 1 1
66 1 1 1
67 1 1 1
68 1 1 1
69 1 1 1
70 1 1 1
71 1 1 1
72 1 1 1
MD.Fixed.XYZ>

scf.XcType GGA-PBE
scf.SpinPolarization off
scf.ElectronicTemperature 300.0
scf.energycutoff 220.0
scf.maxIter 100
scf.EigenvalueSolver band
scf.Kgrid 6 1 1
scf.Mixing.Type rmm-diisk
scf.Init.Mixing.Weight 0.05
scf.Min.Mixing.Weight 0.01
scf.Max.Mixing.Weight 0.30
scf.Mixing.History 25
scf.Mixing.StartPulay 15
scf.criterion 1.0e-7

MD.Type rfc5
MD.maxIter 1000
MD.TimeStep 1.0
MD.Opt.criterion 0.0003

Re: convergence in electric field ( No.4 )

Date: 2023/02/09 02:44
Name: Yung-Ting Lee

Dear maedeh,

(1) RFC5 is a method for optimizing cell vectors and atomic coordinates simultaneously.

The "opt" for geometry optimization may be what you need.

#############
MD.Type opt
#############

(2)

For constrained relaxation, 1 and 0 stand for fixing and relaxing, respectively.

The reference for "Constrained relaxation" can be found in " https://www.openmx-square.org/openmx_man3.8/node53.html ".

In the input that you provided, all atoms are fixed. Due to "rfc5", I guess that only cell vectors change at iteration in your calculation.

Following the input, I recommend the command lines listed below for fixing Sn atoms in the bottom only and relaxing other atoms.

#############
<MD.Fixed.XYZ
1 0 0 1
2 0 0 0
3 0 0 1
4 0 0 0
5 0 0 1
6 0 0 0
7 0 0 1
8 0 0 0
9 0 0 1
10 0 0 0
11 0 0 1
12 0 0 0
13 0 0 1
14 0 0 0
15 0 0 1
16 0 0 0
17 0 0 1
18 0 0 0
19 0 0 1
20 0 0 0
21 0 0 1
22 0 0 0
23 0 0 1
24 0 0 0
25 0 0 1
26 0 0 0
27 0 0 1
28 0 0 0
29 0 0 1
30 0 0 0
31 0 0 1
32 0 0 0
33 0 0 1
34 0 0 0
35 0 0 1
36 0 0 0
37 0 0 1
38 0 0 0
39 0 0 1
40 0 0 0
41 0 0 1
42 0 0 0
43 0 0 1
44 0 0 0
45 0 0 1
46 0 0 0
47 0 0 1
48 0 0 0
49 0 0 1
50 0 0 0
51 0 0 1
52 0 0 0
53 0 0 1
54 0 0 0
55 0 0 1
56 0 0 0
57 0 0 1
58 0 0 0
59 0 0 1
60 0 0 0
61 0 0 0
62 0 0 0
63 0 0 0
64 0 0 0
65 0 0 0
66 0 0 0
67 0 0 0
68 0 0 0
69 0 0 0
70 0 0 0
71 0 0 0
72 0 0 0
MD.Fixed.XYZ>
#############

Please update these command lines and try again.

Best regards,
Yung-Ting Lee

Re: convergence in electric field ( No.5 )

Date: 2023/02/13 23:33
Name: maedeh <mashhadbani.m@gmail.com>

thank you

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