> Dear siesta users, > > I am a green hand. Recently I tried to use siesta to calculate the > phonon band structure of monolayer graphene. But I got a strange > optical phonon dispersion. After I increased the MeshCutoff to 400 Ry, > or PAO.BasisSize to DZP, the shape of the optical phonon dispersion is > still wrong. The following are my input scripts. Would you please > kindly help me to check them. Thank you in advance.
Dear Y. C. Cheng, Are you sure that > SuperCell_1 2 > SuperCell_2 2 suffices to converge real-space force constants? I bet, with higher values the dispersion will change for good. If you cannot afford to increase both values, increase just one (and choose the q-direction correspondingly). Good luck Andrei Postnikov > > test_phonon.in > fcbuild and vibrator > > SystemName graphene > SystemLabel Graphene > NumberOfAtoms 2 > > LatticeConstant 2.46 Ang > > %block LatticeParameters > 1.0 1.0 5.0 90. 90. 120. > %endblock LatticeParameters > > AtomicCoordinatesFormat Fractional > %block AtomicCoordinatesAndAtomicSpecies > 0.000000000 0.000000000 0.500000000 1 12.0107 > 0.333333333 0.666666667 0.500000000 1 12.0107 > %endblock AtomicCoordinatesAndAtomicSpecies > > SuperCell_1 2 > SuperCell_2 2 > SuperCell_3 0 > > AtomicDispl 0.04 Bohr > > BandLinesScale ReciprocalLatticeVectors > %block BandLines > 1 0.00000 0.00000 0.00000 \Gamma > 20 0.00000 0.50000 0.00000 M > 10 0.33333 0.33333 0.00000 K > 15 0.00000 0.00000 0.00000 \Gamma > %endblock BandLines > > test_phonon_siesta.fdf > siesta > SystemName graphene > SystemLabel Graphene > NumberOfSpecies 1 > > LatticeConstant 2.46 Ang > > %block chemicalspecieslabel > 1 6 C > %endblock chemicalspecieslabel > PAO.BasisSize DZP > XC.functional LDA # Exchange-correlation functional type > XC.authors CA # Particular parametrization of xc > func > SpinPolarized .false. # Spin unpolarized calculation > MeshCutoff 300. Ry # Equivalent planewave cutoff for the > grid > MaxSCFIterations 100 # Maximum number of SCF iterations per > step > DM.MixingWeight 0.3 # New DM amount for next SCF cycle > DM.Tolerance 1.d-4 # Tolerance in maximum difference > # between input and output DM > DM.NumberPulay 3 # Number of SCF steps between pulay > mixing > > %include FC.fdf > > > The phonon band structure is also attached. > > > > Best, > -- > Y. C. Cheng > Department of Physics > Nanjing University > Nanjing 210093 > P. R. China > Tel: 86-25-83592907 > Email: [email protected] >
