QE反应路径与NEB

下载完整输入、赝势、真实结果和绘图脚本。解压后，inputs/是可修改输入，reference/是本次真实参考输出，复跑结果写入 work/。下面的计算命令在已分配的相应资源内运行。

1 H＋H₂交换反应#

本例用线性H₃的7个图像演示CI-NEB。中间H固定，外侧H仅沿x方向移动；初末端和内部图像都参与优化。盒长12 Bohr、固定双重态、40/200 Ry，属于有限周期盒中的受约束路径，不是包含隧穿、零点能和自由能校正的实验反应势垒。

cat inputs/h3-neb-relaxed/neb.in
bash run.sh h3-neb-relaxed
grep "convergence achieved" work/h3-neb-relaxed/neb.in.out
cat work/h3-neb-relaxed/h3.dat

2 完整NEB输入#

! This is a comment
# This is another one
BEGIN
BEGIN_PATH_INPUT
&PATH
  restart_mode      = 'from_scratch'
  string_method     = 'neb',
  nstep_path        = 80,
  ds                = 2.D0,
  opt_scheme        = "broyden",
  num_of_images     = 7,
  k_max             = 0.3D0,
  k_min             = 0.2D0,
  CI_scheme         = "auto",
  path_thr          = 0.02D0,
  first_last_opt=.true.,
/
END_PATH_INPUT
BEGIN_ENGINE_INPUT
&CONTROL
  prefix         = "h3",
  pseudo_dir="../pseudo",outdir="./tmp",
/
&SYSTEM
  ibrav                  = 0,
  nat                    = 3,
  ntyp                   = 1,
  ecutwfc                = 40.0D0,
  ecutrho                = 200.0D0,
  nspin                  = 2,
  tot_magnetization      = 1,
  occupations            = "fixed",

/
&ELECTRONS
  conv_thr    = 1.D-8,
  mixing_beta = 0.3D0,
/
&IONS
/
ATOMIC_SPECIES
H  1.00794  HUSPBE.RRKJ3
BEGIN_POSITIONS
FIRST_IMAGE
ATOMIC_POSITIONS { bohr }
H   -4.56670009      0.00000000      0.00000000  1  0  0
H    0.00000000      0.00000000      0.00000000  0  0  0
H    1.55776676      0.00000000      0.00000000  1  0  0
LAST_IMAGE
ATOMIC_POSITIONS { bohr }
H   -1.55776676      0.00000000      0.00000000
H    0.00000000      0.00000000      0.00000000
H    4.56670009      0.00000000      0.00000000
END_POSITIONS
K_POINTS { gamma }
CELL_PARAMETERS { bohr }
  12.00000  0.00000  0.00000
   0.00000 12.00000  0.00000
   0.00000  0.00000 12.00000
END_ENGINE_INPUT
END

num_of_images=7包含两端；CI_scheme=auto自动选择爬山图像；path_thr单位eV/Å。first_last_opt=.true.明确允许两端优化，避免用尚未松弛的端点当作反应能零点。FIRST_IMAGE行末的1/0控制方向自由度，与路径优化本身是两种约束。

3 实际路径与几何#

本次39次路径迭代收敛，最大路径力0.019428 eV/Å，端点也低于0.02 eV/Å。正向势垒0.174238 eV，反向在数值精度内对称。鞍点附近两个H–H距离约0.9357 Å。

4 检查和复用#

grep -A11 "image.*energy" work/h3-neb-relaxed/neb.in.out | tail -n 12
module load calorine/4.0
python extract.py neb
python plot.py
ls qe-neb.png qe-neb-structures.png

h3.dat的第一列是归一化路径长度，第二列是相对初态能量，第三列是路径误差/力。若端点未优化，应另外检查端点是否为局部极小；只看爬山图像的力不够。更换反应时保持原子顺序一致，避免插值跨周期边界形成重叠，随后检查图像数、盒子、k点、磁性和泛函。化学势垒还可能需要零点与热自由能修正。