前言
对于二维材料，如何固定z方向晶胞参数不变（固定z轴），优化x、y晶胞参数呢？
下载所有方案。
网上解决方法的原理接近，主要是修改constr_cell_relax.F文件，按发布时间顺序可分三种：
方案一
2018-03-19 chempeng 《VASP固定基矢优化结构》
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
|
!-----------------------------------------------------------------------
!
! At present, VASP does not allow to relax the cellshape selectively
! i.e. for instance only cell relaxation in x direction.
! To be more precisse, this behaviour can not be achived via the INCAR
! or POSCAR file.
! However, it is possible to set selected components of the stress tensor
! to zero.
! The most conveninent position to do this is the routines
! CONSTR_CELL_RELAX (constraint cell relaxation).
! FCELL contains the forces on the basis vectors.
! These forces are used to modify the basis vectors according
! to the following equations:
!
! A_OLD(1:3,1:3)=A(1:3,1:3) ! F90 style
! DO J=1,3
! DO I=1,3
! DO K=1,3
! A(I,J)=A(I,J) + FCELL(I,K)*A_OLD(K,J)*STEP_SIZE
! ENDDO
! ENDDO
! ENDDO
! where A holds the basis vectors (in cartesian coordinates).
!
!-----------------------------------------------------------------------
SUBROUTINE CONSTR_CELL_RELAX(FCELL)
USE prec
REAL(q) FCELL(3,3)
DO I=1,3
! fix z
FCELL(3,I)=0
FCELL(I,3)=0
! ! fix x
! FCELL(1,I)=0
! FCELL(I,1)=0
! ! fix y
! FCELL(2,I)=0
! FCELL(I,2)=0
ENDDO
! just one simple example
! relaxation in x directions only
! SAVE=FCELL(1,1)
! FCELL=0 ! F90 style: set the whole array to zero
! FCELL(1,1)=SAVE
! relaxation in z direction only
! SAVE=FCELL(3,3)
! FCELL=0 ! F90 style: set the whole array to zero
! FCELL(3,3)=SAVE
RETURN
END SUBROUTINE
|
- 固定z轴，弛豫x、y轴。若以WSe2为例，
POSCAR为，
1
2
3
4
5
6
7
8
9
10
11
12
13
14
|
Se2 W
1.0
3.2899999619 0.0000000000 0.0000000000
-1.6449999809 2.8492235454 0.0000000000
0.0000000000 0.0000000000 12.9700002670
W Se
2 4
Direct
0.333333343 0.666666687 0.250000000
0.666666627 0.333333313 0.750000000
0.333333343 0.666666687 0.620999992
0.666666627 0.333333313 0.379000008
0.666666627 0.333333313 0.120999992
0.333333343 0.666666687 0.879000008
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
|
Se2 W
1.00000000000000
3.2988809157024286 -0.0000009118894020 0.0000000000000000
-1.6494412476071403 2.8569140950044987 0.0000000000000000
0.0000000000000000 0.0000000000000000 12.9700002669999996
W Se
2 4
Direct
0.3333332795709047 0.6666667206026287 0.2499999920982164
0.6666666936724241 0.3333332807801080 0.7499999970341932
0.3333333290727808 0.6666666860461303 0.6193498945590813
0.6666666393043650 0.3333333132884654 0.3806501104445901
0.6666666352755654 0.3333333096490192 0.1193498971153154
0.3333333331039529 0.6666666896336484 0.8806501087486037
0.00000000E+00 0.00000000E+00 0.00000000E+00
0.00000000E+00 0.00000000E+00 0.00000000E+00
0.00000000E+00 0.00000000E+00 0.00000000E+00
0.00000000E+00 0.00000000E+00 0.00000000E+00
0.00000000E+00 0.00000000E+00 0.00000000E+00
0.00000000E+00 0.00000000E+00 0.00000000E+00
|
方案二（推荐）
2018-05-20 Chengcheng-Xiao 《VASP_OPT_AXIS》
2018-09-06 Mr.ZhengGang 《VASP固定晶胞方向不优化》
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
|
SUBROUTINE CONSTR_CELL_RELAX(FCELL)
USE PREC
REAL(Q) FCELL(3,3), SAVE(3)
LOGICAL FILFLG
INTEGER ICELL(3)
INQUIRE(FILE='OPTCELL',EXIST=FILFLG)
IF (FILFLG) THEN
OPEN(67,FILE='OPTCELL',FORM='FORMATTED',STATUS='OLD')
READ(67,"(3I1)") (ICELL(I),I=1,3)
CLOSE(67)
DO I=1,3
SAVE(I)=FCELL(I,I)
ENDDO
FCELL=0.0d0
DO I=1,3
IF (ICELL(I)==1) FCELL(I,I)=SAVE(I)
ENDDO
ENDIF
! just one simple example
! relaxation in x directions only
! SAVE=FCELL(1,1)
! FCELL=0 ! F90 style: set the whole array to zero
! FCELL(1,1)=SAVE
RETURN
END SUBROUTINE
|
1
|
110 #1表示优化，0表示不优化；三个数字依次对应于xyz方向。比如 110 表示z轴不优化；001 表示x和y轴都不优化。
|
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
|
Se2 W
1.00000000000000
3.2988809154146170 0.0000000000000000 0.0000000000000000
-1.6494404576571737 2.8569136389682201 0.0000000000000000
0.0000000000000000 0.0000000000000000 12.9700002669999996
W Se
2 4
Direct
0.3333332763757423 0.6666667206116557 0.2499999920871069
0.6666666968682680 0.3333332807560439 0.7499999970274550
0.3333333274478362 0.6666666860442724 0.6193498945625138
0.6666666409113122 0.3333333132431017 0.3806501104629225
0.6666666368917313 0.3333333096672763 0.1193498970910784
0.3333333315051024 0.6666666896776502 0.8806501087689232
0.00000000E+00 0.00000000E+00 0.00000000E+00
0.00000000E+00 0.00000000E+00 0.00000000E+00
0.00000000E+00 0.00000000E+00 0.00000000E+00
0.00000000E+00 0.00000000E+00 0.00000000E+00
0.00000000E+00 0.00000000E+00 0.00000000E+00
0.00000000E+00 0.00000000E+00 0.00000000E+00
|
注意
Chengcheng-Xiao VASP_OPT_AXIS还可以对xx xy xz yx yy yz zx zy zz方向进行固定或弛豫。
方案三
2019-05-05 Jincheng Liu 《VASP固定基矢优化结构方法》
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
|
Se2 W
1.00000000000000
3.2988809156770467 -0.0000009123103790 0.0000000000000000
-1.6494412475791849 2.8569140951081820 0.0000000000000000
0.0000000000000000 0.0000000000000000 12.9700002669999996
W Se
2 4
Direct
0.3333332795922008 0.6666667206713092 0.2499999920944698
0.6666666936429270 0.3333332808269298 0.7499999970276957
0.3333333290707461 0.6666666860010831 0.6193498945606164
0.6666666392590765 0.3333333132864525 0.3806501104582833
0.6666666352395026 0.3333333095723708 0.1193498971142689
0.3333333331955395 0.6666666896418546 0.8806501087446658
0.00000000E+00 0.00000000E+00 0.00000000E+00
0.00000000E+00 0.00000000E+00 0.00000000E+00
0.00000000E+00 0.00000000E+00 0.00000000E+00
0.00000000E+00 0.00000000E+00 0.00000000E+00
0.00000000E+00 0.00000000E+00 0.00000000E+00
0.00000000E+00 0.00000000E+00 0.00000000E+00
|
