```python
from pyscf import gto, scf, cc, pbc
import numpy as np

# Define the cell
cell = pbc.gto.Cell()
cell.atom = 'C 0 0 0; C 1.42 1.42 0'
cell.basis = 'gth-szv'
cell.pseudo = 'gth-pade'
cell.a = np.eye(3) * 2.84
cell.unit = 'B'
cell.build()

# KHF and KCCSD with 2x2x2 k-points
kpts = cell.make_kpts([2, 2, 2])
khf = scf.KRHF(cell, kpts=kpts).density_fit()
khf.kernel()
kccsd = cc.KCCSD(khf)
kccsd.kernel()
print("Total energy per unit cell (2x2x2 k-points):", kccsd.e_tot)

# KHF and KCCSD for a single k-point
kpts = cell.make_kpts([1, 1, 1])
khf = scf.KRHF(cell, kpts=kpts).density_fit()
khf.kernel()
kccsd = cc.KCCSD(khf)
kccsd.kernel()
print("Total energy per unit cell (single k-point):", kccsd.e_tot)

# Single k-point calculation using RHF
rhf = scf.RHF(cell).density_fit()
rhf.kernel()
rccsd = cc.RCCSD(rhf)
rccsd.kernel()
print("Total energy per unit cell at the k-point (RCCSD):", rccsd.e_tot)
print("RCCSD energy based on CCSD density matrices:", rccsd.ccsd_t())

# Convert RHF to UHF and run UCCSD
uhf = rhf.to_uhf()
uccsd = cc.UCCSD(uhf)
uccsd.kernel()
print("Total energy per unit cell at the k-point (UCCSD):", uccsd.e_tot)
print("UCCSD energy based on CCSD density matrices:", uccsd.ccsd_t())

# Convert UHF to GHF and run GCCSD
ghf = uhf.to_ghf()
gccsd = cc.GCCSD(ghf)
gccsd.kernel()
print("Total energy per unit cell at the k-point (GCCSD):", gccsd.e_tot)
print("GCCSD energy based on CCSD density matrices:", gccsd.ccsd_t())
```