Dear Andrei, > 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). >
I increased SuperCell_1 and SuperCell_2 to 3. But the results are almost the same. Any other suggestion? Best, Yingchun Cheng 2010/9/18 <[email protected]>: >> 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] >> > > -- Y. C. Cheng Department of Physics Nanjing University Nanjing 210093 P. R. China Tel: 86-25-83592907 Email: [email protected]
