For Berry phase calculation: direction of the k-point strings in reciprocal space. For Berry phase calculation: number of k-points to be calculated along each symmetry-reduced string. NB: - The total energy displayed in 'prefix. Details of the monopole potential can be found in T.
Brumme, M. Calandra, F. Mauri; PRB 89, Note, that in systems which are not symmetric with respect to the plate, one needs to enable the dipole correction! Bravais-lattice index.
Crystallographic constants - see the ibrav variable. Only needed values depending on ibrav must be specified. Number of electronic states bands to be calculated. Note that in spin-polarized calculations the number of k-point, not the number of bands per k-point, is doubled.
Total charge of the system. Useful for simulations with charged cells. In a periodic calculation a compensating jellium background is inserted to remove divergences if the cell is not neutral. Total majority spin charge - minority spin charge. Used to impose a specific total electronic magnetization. Starting spin polarization on atomic type 'i' in a spin polarized calculation. Values range between -1 all spins down for the valence electrons of atom type 'i' to 1 all spins up.
Breaks the symmetry and provides a starting point for self-consistency. Note that if you start from zero initial magnetization, you will invariably end up in a nonmagnetic zero magnetization state. If you want to start from an antiferromagnetic state, you may need to define two different atomic species corresponding to sublattices of the same atomic type.
The magnetization is never calculated and kept zero the internal variable domag is. Kinetic energy cutoff Ry for charge density and potential For norm-conserving pseudopotential you should stick to the default value, you can reduce it by a little but it will introduce noise especially on forces and stress. The use of gradient-corrected functional, especially in cells with vacuum, or for pseudopotential without non-linear core correction, usually requires an higher values of ecutrho to be accurately converged.
Kinetic energy cutoff Ry for the exact exchange operator in EXX type calculations. By default this is the same as ecutrho but in some EXX calculations significant speed-up can be found by reducing ecutfock, at the expense of some loss in accuracy. Must be. Not implemented for stress calculation. Use with care, especially in metals where it may give raise to instabilities. Three-dimensional FFT mesh hard grid for charge density and scf potential.
If not specified the grid is calculated based on the cutoff for charge density see also ecutrho Note: you must specify all three dimensions for this setting to be used. Three-dimensional mesh for wavefunction FFT and for the smooth part of charge density smooth grid.
A careful usage of this option can be advantageous: - in low-symmetry large cells, if you cannot afford a k-point grid with the correct symmetry - in MD simulations - in calculations for isolated atoms. The same applies if a k-point list is provided in input instead of a Monkhorst-Pack grid. This option differs from nosym because it forces k-points in all cases to have the full symmetry of the Bravais lattice not all uniform grids have such property! These operations are incompatible with real-space symmetrization but not with the new G-space symmetrization.
Both still use symmetrization in real space. Available options are: 'smearing' : gaussian smearing for metals; see variables smearing and degauss 'tetrahedra' : Tetrahedron method, Bloechl's version: P. To be used only as a reference; the optimized tetrahedron method is more efficient. Kawamura, PRB 89, Can be used for phonon calculations as well. Option valid only for a single k-point, requires nbnd to be set in input. If it is. The occupations indicate which atomic states are filled.
The order of the states is written inside the UPF pseudopotential file. Up and down is relative to the direction of the starting magnetization. When lspinorb is. D0 Ry. Available options are: 'gaussian' , 'gauss' : ordinary Gaussian spreading Default 'methfessel-paxton' , 'm-p' , 'mp' : Methfessel-Paxton first-order spreading see PRB 40, Bernasconi et al, J. Solids 56, , doi Overrides the value read from pseudopotential files.
Use with care and if you know what you are doing! Fraction of EXX for hybrid functional calculations. For more information, see: J. Specific for EXX. It selects the kind of approach to be used for treating the Coulomb potential divergencies at small q vectors. Reciprocal space cutoff for correcting Coulomb potential divergencies at small q vectors.
Three-dimensional mesh for q k1-k2 sampling of the Fock operator EXX. Can be smaller than the number of k-points. Currently this defaults to the size of the k-point mesh used. D0 for all species. See also PRB 84, If B or E2 or E3 are not specified or set to 0 they will be calculated from J using atomic ratios. Leave unchanged eigenvalues that are not set.
This is useful to suggest the desired orbital occupations when the default choice takes another path. Currently available choices: 'atomic' : use atomic wfc's as they are to build the projector 'ortho-atomic' : use Lowdin orthogonalized atomic wfc's 'norm-atomic' : Lowdin normalization of atomic wfc.
Keep in mind: atomic wfc are not orthogonalized in this case. This is a "quick and dirty" trick to be used when atomic wfc from the pseudopotential are not normalized and thus produce occupation whose value exceeds unity. If orthogonalized wfc are not needed always try 'atomic' first. The charge density outside the atomic core radii is excluded. NB: forces and stress currently implemented only for the 'atomic' and 'pseudo' choice. Used only if tefield is.
Zone in the unit cell where the saw-like potential decreases. Important: the change of slope of this potential must be located in the empty region, or else unphysical forces will result. The angle expressed in degrees between the initial magnetization and the z-axis. For noncollinear calculations only; index i runs over the atom types. The angle expressed in degrees between the projection of the initial magnetization on x-y plane and the x-axis.
For noncollinear calculations only. Used to perform constrained calculations in magnetic systems. Lambda is a real number see below. Noncolinear case only. Try not to start with very highly symmetric configurations or use the nosym flag only as a last remedy. Number of iterations after which the program writes all the atomic magnetic moments.
Used to perform calculation assuming the system to be isolated a molecule or a cluster in a 3D supercell. An estimate of the vacuum level is also calculated so that eigenvalues can be properly aligned.
Theory: G. Makov, and M. Payne, "Periodic boundary conditions in ab initio calculations" , PRB 51, Adapted from: G. Martyna, and M. Tuckerman, "A reciprocal space based method for treating long range interactions in ab-initio and force-field-based calculation in clusters", J. For polarized or charged slab calculation, embeds the simulation cell within an effective semi- infinite medium in the perpendicular direction along z. Method described in M.
Otani and O. Sugino, "First-principles calculations of charged surfaces and interfaces: A plane-wave nonrepeated slab approach", PRB 73, NB: - Two dimensional xy plane average charge density and electrostatic potentials are printed out to 'prefix. Currently available choices: 'pbc' : default : regular periodic calculation no ESM.
Type of Van der Waals correction. Grimme, J. Barone et al. Tkatchenko and M. Scheffler, PRL , Becke et al. Otero de la Roza et al. Default is good for PBE. Optional: controls the convergence of the vdW energy and forces. The default value is a safe choice, likely too safe, but you do not gain much in increasing it.
Optional: set it to. Damping function parameter a1 adimensional. This value should change with the exchange-correlation functional. The charge density outside the atomic core radii is excluded. NB: forces and stress currently implemented only for the 'atomic' and 'pseudo' choice. Requires compilation with hdf5 support. If true, nscf calculation will exit in restart mode, scf calculation will restart from there if DMFT updates are provided as hdf5 archive. PBE correlation ratios after each converged electronic ground state calculation.
Ensemble energies can be analyzed with the 'bee' utility included with libbeef. Requires linking against libbeef. Used only if tefield is. Zone in the unit cell where the saw-like potential decreases. Important: the change of slope of this potential must be located in the empty region, or else unphysical forces will result.
The angle expressed in degrees between the initial magnetization and the z-axis. For noncollinear calculations only; index i runs over the atom types. The angle expressed in degrees between the projection of the initial magnetization on x-y plane and the x-axis.
For noncollinear calculations only. When starting a non collinear calculation using an existing density file from a collinear lsda calculation assumes previous density points in z direction and rotates it in the direction described by angle1 and angle2 variables for atomic type 1. Used to perform constrained calculations in magnetic systems. Lambda is a real number see below. Noncolinear case only. Try not to start with very highly symmetric configurations or use the nosym flag only as a last remedy.
Used to perform calculation assuming the system to be isolated a molecule or a cluster in a 3D supercell. An estimate of the vacuum level is also calculated so that eigenvalues can be properly aligned. Theory: G. Makov, and M. Payne, "Periodic boundary conditions in ab initio calculations" , PRB 51, Adapted from: G. Martyna, and M. Tuckerman, "A reciprocal space based method for treating long range interactions in ab-initio and force-field-based calculation in clusters", J.
For polarized or charged slab calculation, embeds the simulation cell within an effective semi- infinite medium in the perpendicular direction along z. Method described in M. Otani and O. Sugino, "First-principles calculations of charged surfaces and interfaces: A plane-wave nonrepeated slab approach", PRB 73, NB: - Two dimensional xy plane average charge density and electrostatic potentials are printed out to 'prefix.
Total energy, forces and stresses are computed in a two-dimensional framework. Linear-response calculations done on top of a self-consistent calculation with this flag will automatically be performed in the 2D framework as well. Please refer to: Sohier, T. NB: - The length of the unit-cell along the z direction should be larger than twice the thickness of the 2D material including electrons.
A reasonable estimate for a layer's thickness could be the interlayer distance in the corresponding layered bulk material. Currently available choices: 'pbc' : default : regular periodic calculation no ESM. JCP , , R. Sundararaman, et al.
Larger values are recommended, if systems with small DOS on Fermi surface as graphite. Type of Van der Waals correction. Grimme, J. Barone et al. Grimme et al, J.
Phys , , doi Tkatchenko and M. Scheffler, PRL , Ambrosetti, A. Reilly, R. DiStasio, A. Tkatchenko, J. Becke et al. Otero de la Roza et al. Default is good for PBE. Turn three-body terms in Grimme-D3 on.
Optional: controls the convergence of the vdW energy and forces. The default value is a safe choice, likely too safe, but you do not gain much in increasing it. Optional: set it to. Damping function parameter a1 adimensional. Otero de la Roza, E. Johnson, J. Damping function parameter a2 angstrom. This allows to give in input only the inequivalent atomic positions. The positions of all the symmetry equivalent atoms are calculated by the code.
Used only for monoclinic lattices. Used only for space groups that in the ITA allow the use of two different origins.
Used only for rhombohedral space groups. In units of the unit cell length in z direction, zgate in ]0,1[ Details of the gate potential can be found in T. Allows the relaxation of the system towards the charged plate.
Height of the potential barrier in Rydberg. Use with care. Available options are: 'plain' : charge density Broyden mixing 'TF' : as above, with simple Thomas-Fermi screening for highly homogeneous systems 'local-TF' : as above, with local-density-dependent TF screening for highly inhomogeneous systems.
If you are tight with memory, you may reduce it to 4 or so. Available options are: 'david' : Davidson iterative diagonalization with overlap matrix default. Fast, may in some rare cases fail. MUCH slower than 'david' but uses less memory and is a little bit more robust. Convergence threshold ethr for iterative diagonalization the check is on eigenvalue convergence. For scf calculations: default is 1.
D-2 if starting from a superposition of atomic orbitals; 1. D-5 if starting from a charge density. During self consistency the threshold is automatically reduced but never below 1. D when approaching convergence. For conjugate gradient diagonalization: max number of iterations. For Davidson diagonalization: dimension of workspace number of wavefunction packets, at least 2 needed.
Otherwise the empty states are diagonalized using a larger threshold this should not affect total energy, forces, and other ground-state properties.
Amplitude of the finite electric field in Ry a. D0, 0. Finite electric field in Ry a. Available options are: 'atomic' : Start from superposition of atomic orbitals. If not enough atomic orbitals are available, fill with random numbers the remaining wfcs The scf typically starts better with this option, but in some high-symmetry cases one can "loose" valence states, ending up in the wrong ground state. Prevents the "loss" of states mentioned above.
Slower start of scf but safe. Faster but numerically less accurate than the default G-space algorithm. Use with care and after testing! Faster and in principle better scaling than the default G-space algorithm, but numerically less accurate, may lead to some loss of translational invariance. Available options are: 'default' : if restarting, use atomic positions read from the restart file; in all other cases, use atomic positions from standard input.
Initial ionic velocities. Specify the type of ionic dynamics. Rossky, JCP, 69, , doi Used to extrapolate the potential from preceding ionic steps. Used to extrapolate the wavefunctions from preceding ionic steps. If set to true the total torque of the internal forces is set to zero by adding new forces that compensate the spurious interaction with the periodic images. This allows for the use of smaller supercells. BEWARE: since the potential energy is no longer consistent with the forces it still contains the spurious interaction with the repeated images , the total energy is not conserved anymore.
However the dynamical and thermodynamical properties should be in closer agreement with those of an isolated system. Also the final energy of a structural relaxation will be higher, but the relaxation itself should be faster. Available options are: 'rescaling' : control ionic temperature via velocity rescaling first method see parameters tempw , tolp , and nraise for VC-MD only.
The temperature is controlled via velocitiy rescaling. Starting temperature Kelvin in MD runs target temperature for most thermostats. Tolerance for velocity rescaling. Velocities are rescaled if the run-averaged and target temperature differ more than tolp.
This is the temperature reported in the main output. This keyword applies only in the case of molecular dynamics or damped dynamics. If true the ions are refolded at each step into the supercell. Number of old forces and displacements vectors used in the PULAY mixing of the residual vectors obtained on the basis of the inverse hessian matrix given by the BFGS algorithm. Maximum ionic displacement in the structural relaxation. Initial ionic displacement in the structural relaxation. Parameters used in line search based on the Wolfe conditions.
Initial value of the alpha mixing factor in the FIRE minimization scheme; recommended values are between 0. Factor for increasing dt. Factor for decreasing dt. Specify the type of dynamics for the cell. Target pressure [KBar] in a variable-cell md or relaxation run.
Fictitious cell mass [amu] for variable-cell simulations both 'vc-md' and 'vc-relax'. Used in the construction of the pseudopotential tables. It should exceed the maximum linear contraction of the cell during a simulation.
Convergence threshold on the pressure for variable cell relaxation 'vc-relax' : note that the other convergence thresholds for ionic relaxation apply as well.
Select which of the cell parameters should be moved: 'all' : all axis and angles are moved 'ibrav' : all axis and angles are moved, but the lattice remains consistent with the initial ibrav choice. Please note that some combinations do not make sense for some crystals and will guarantee that the relax will never converge. The target Fermi energy eV. Convergence threshold on force eV for FCP relaxation.
Variables used for FCP dynamics. Mass of the FCP. Initial velocity of the FCP.
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