Table 1 Optimized geometry, charge (Qring), frequency (ν 1 ) and HOMO-LUMO gap of molecules 1–10 at the B3LYP/cc-pVTZ level.

From: Flat building blocks for flat silicene

Molecule

Bond lengtha/Å

Qring b

ν 1 c /cm−1

H-L gapd/eV

1

2.252/r1

−2.2

47.57

1.90 (2.60)

2

2.267/r1, 2.234/r2, 2.267/r3, 2.266/r4

−3.0

22.22

1.61 (1.94)

3

2.274/r1, 2.229/r2, 2.274/r3, 2.250/r4, 2.274/r5

−3.8

13.41

1.21 (1.51)

4

2.248/r1, 2.252/r2, 2.280/r3, 2.222/r4, 2.263/r5

−3.8

15.26

1.39 (1.58)

5

2.231/r1, 2.268/r2, 2.255/r3, 2.263/r4

−4.6

14.80

1.24(1.71)

6

1.391/r1

−1.2

413.94

5.47 (6.70)

7

1.412/r1, 1.370/r2, 1.416/r3, 1.428/r4

−1.6

173.54

4.39 (4.79)

8

1.421/r1, 1.363/r2, 1.425/r3, 1.395/r4, 1.440/r5

−2.0

91.43

3.22 (3.57)

9

1.388/r1, 1.399/r2, 1.433/r3, 1.355/r4, 1.423/r5

−2.0

99.20

3.68 (3.84)

10

1.366/r1, 1.419/r2, 1.416/r3, 1.423/r4

−2.4

88.27

3.22 (4.03)

  1. aThe notation r1−r5 represents the bond length between the X atoms (X = Si, C) shown in Fig. 3. bQring: Summation of the NPA charges on the ring. c ν 1 : The lowest vibrational frequency. dHOMO-LUMO gap from the first excitation energies obtained by TDDFT/B3LYP. HOMO-LUMO gap from the Kohn-Sham eigenvalues of the ground state DFT/B3LYP calculation is given in parentheses.
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