VASP计算H2分子的结合能
VASP计算H2分子的结合能
首先要计算一个氢气分子的孤立能量,再减去两个孤立氢原子能量,将得到氢气分子的结合能。
1. 先计算单个原子能量,POTCAR选取PAW_GGA
INCAR:
PREC=Accurate
ISMEAR=0; SIGMA=0.05
ISPIN=2
KPOINTS:
Monkhorst Pack
0
Monkhorst Pack
1 1 1
0 0 0
POSCAR:
H atom
1
15.0 0.0 0.0
0.0 15.0 0.0
0.0 0.0 15.0
H
1
Cart
0 0 0
得到的能量如下:
Free energy of the ion-electron system (eV)
---------------------------------------------------
alpha Z PSCENC = 0.00072437
Ewald energy TEWEN = -1.36188267
-1/2 Hartree DENC = -6.92165960
-V(xc)+E(xc) XCENC = 2.34398347
PAW double counting = 0.74203130 -0.75105109
entropy T*S EENTRO = 0.00000000
eigenvalues EBANDS = -7.60619631
atomic energy EATOM = 12.44420649
---------------------------------------------------
free energy TOTEN = -1.10984404 eV
energy without entropy = -1.10984404 energy(sigma->0) = -1.10984404
2. 计算H2分子的能量
INCAR:
PREC=Accurate
ISMEAR=0; SIGMA=0.05
ISPIN=2
NSW=5
IBRION=2
POTIM=0.1
KPOINTS
Monkhorst Pack
0
Monkhorst Pack
1 1 1
0 0 0
POSCAR:
H2 molecular
1
8.0 0.0 0.0
0.0 8.0 0.0
0.0 0.0 8.0
H
2
Cart
0 0 0
0 0 0.5
得到的能量如下:
Free energy of the ion-electron system (eV)
---------------------------------------------------
alpha Z PSCENC = 0.01909948
Ewald energy TEWEN = 9.03591211
-1/2 Hartree DENC = -25.32819184
-V(xc)+E(xc) XCENC = 5.31187543
PAW double counting = 8.66129443 -8.70651972
entropy T*S EENTRO = 0.00000000
eigenvalues EBANDS = -20.61147888
atomic energy EATOM = 24.88841298
---------------------------------------------------
free energy TOTEN = -6.72959600 eV
energy without entropy = -6.72959600 energy(sigma->0) = -6.72959600
得到的CONTCAR文件如下:
H2 molecular
1.00000000000000
8.0000000000000000 0.0000000000000000 0.0000000000000000
0.0000000000000000 8.0000000000000000 0.0000000000000000
0.0000000000000000 0.0000000000000000 8.0000000000000000
2
Direct
0.0000000000000000 0.0000000000000000 -0.0155839976608132
0.0000000000000000 0.0000000000000000 0.0780839976608132
0.00000000E+00 0.00000000E+00 0.00000000E+00
0.00000000E+00 0.00000000E+00 0.00000000E+00
3. 计算得到结合能
键能计算:
E
=
−
(
TOTEN
(
H
2
)
−
2
×
TOTEN
(
H
)
)
=
−
(
−
6.72959600
−
2
×
−
1.10984404
)
=
4.51
eV
E = -\left( \text{TOTEN}(\text{H}_2) - 2 \times \text{TOTEN}(\text{H}) \right) = -\left( -6.72959600 - 2 \times -1.10984404 \right) = 4.51 \ \text{eV}
E=−(TOTEN(H2)−2×TOTEN(H))=−(−6.72959600−2×−1.10984404)=4.51 eV
H-H键长计算:
r
=
(
x
2
−
x
1
)
2
+
(
y
2
−
y
1
)
2
+
(
z
2
−
z
1
)
2
=
(
0.0780839976608132
+
0.0155839976608132
)
×
8
=
0.74934
A
˚
r = \sqrt{(x_2 - x_1)^2 + (y_2 - y_1)^2 + (z_2 - z_1)^2} = \left( 0.0780839976608132 + 0.0155839976608132 \right) \times 8 = 0.74934 \ \text{Å}
r=(x2−x1)2+(y2−y1)2+(z2−z1)2=(0.0780839976608132+0.0155839976608132)×8=0.74934 A˚
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