C

Name CalcInfrared
Section Linear Response::Vibrational Modes
Type logical
Default true

If set to true, infrared intensities (and born charges) will be calculated and written in vib_modes/infrared.

Name CalcNormalModeWfs
Section Linear Response::Vibrational Modes
Type logical
Default false

If set to true, the response wavefunctions for each normal mode will be calculated and written in directory restart/vib_modes/phn_nm_wfs_XXXXX. This part is time-consuming and not parallel, but not needed for most purposes.

Name CalculateDiamagneticCurrent
Section Hamiltonian
Type logical
Default no

This variable decides whether the current density arising from the non-uniform vector potential, defined as: $ \vec{J}_{dmc}(\vec{r}, t)=-\frac{e^2}{m_e c_0} n(\vec{r}, t) \vec{A}(\vec{r},t)$ $ is included in the total current density.

Name CalculateSelfInducedMagneticField
Section Hamiltonian
Type logical
Default no

The existence of an electronic current implies the creation of a self-induced magnetic field, which may in turn back-react on the system. Of course, a fully consistent treatment of this kind of effect should be done in QED theory, but we will attempt a first approximation to the problem by considering the lowest-order relativistic terms plugged into the normal Hamiltonian equations (spin-other-orbit coupling terms, etc.). For the moment being, none of this is done, but a first step is taken by calculating the induced magnetic field of a system that has a current, by considering the magnetostatic approximation and Biot-Savart law:

$ \nabla^2 \vec{A} + 4\pi\alpha \vec{J} = 0$

$ \vec{B} = \vec{\nabla} \times \vec{A}$

If CalculateSelfInducedMagneticField is set to yes, this B field is calculated at the end of a gs calculation (nothing is done – yet – in the tdcase) and printed out, if the Output variable contains the potential keyword (the prefix of the output files is Bind).

Name CalculationMode
Section Calculation Modes
Type integer
Default gs

Decides what kind of calculation is to be performed.

Options:

• gs:
  Calculation of the ground state.
  
• unocc:
  Calculation of unoccupied/virtual KS states. Can also be used for a non-self-consistent calculation of states at arbitrary k-points, if density.obf from gs is provided in the restart/gs directory.
  
• td:
  Time-dependent calculation (experimental for periodic systems).
  
• go:
  Optimization of the geometry.
  
• opt_control:
  Optimal control.
  
• em_resp:
  Calculation of the electromagnetic response: electric polarizabilities and hyperpolarizabilities and magnetic susceptibilities (experimental for periodic systems).
  
• casida:
  Excitations via Casida linear-response TDDFT; for finite systems only.
  
• vdw:
  Calculate van der Waals coefficients.
  
• vib_modes:
  Calculation of the vibrational modes.
  
• one_shot:
  Obsolete. Use gs with MaximumIter = 0 instead.
  
• kdotp:
  Calculation of effective masses by $\vec{k} \cdot \vec{p}$ perturbation theory (experimental).
  
• dummy:
  This calculation mode does nothing. Useful for debugging, testing and benchmarking.
  
• invert_ks:
  Invert the Kohn-Sham equations (experimental).
  
• test:
  
• recipe:
  Prints out a tasty recipe.
  

Name CasidaCalcForces
Section Linear Response::Casida
Type logical
Default false

(Experimental) Enable calculation of excited-state forces. Requires previous vib_modes calculation.

Name CasidaCalcForcesKernel
Section Linear Response::Casida
Type logical
Default true

If false, the derivative of the kernel will not be included in the excited-state force calculation.

Name CasidaCalcForcesSCF
Section Linear Response::Casida
Type logical
Default false

If true, the ground-state forces will be included in the excited-state forces, so they are total forces. If false, the excited-state forces that are produced are only the gradients of the excitation energy.

Name CasidaCalcTriplet
Section Linear Response::Casida
Type logical
Default false

For a non-spin-polarized ground state, singlet or triplet excitations can be calculated using different matrix elements. Default is to calculate singlets. This variable has no effect for a spin-polarized calculation.

Name CasidaDistributedMatrix
Section Linear Response::Casida
Type logical
Default false

Large matrices with more than a few thousand rows and columns usually do not fit into the memory of one processor anymore. With this option, the Casida matrix is distributed in block-cyclic fashion over all cores in the ParOther group. The diagonalization is done in parallel using ScaLAPACK or ELPA, if available. For very large matrices (>100000), only the ParOther strategy should be used because the diagonalization dominates the run time of the computation.

Name CasidaHermitianConjugate
Section Linear Response::Casida
Type logical
Default false

The Casida matrix is Hermitian, so it should not matter whether we calculate the upper or lower diagonal. Numerical issues may cause small differences however. Use this variable to calculate the Hermitian conjugate of the usual matrix, for testing.

Name CasidaKohnShamStates
Section Linear Response::Casida
Type string
Default all states

The calculation of the excitation spectrum of a system in the Casida frequency-domain formulation of linear-response time-dependent density functional theory (TDDFT) implies the use of a basis set of occupied/unoccupied Kohn-Sham orbitals. This basis set should, in principle, include all pairs formed by all occupied states, and an infinite number of unoccupied states. In practice, one has to truncate this basis set, selecting a number of occupied and unoccupied states that will form the pairs. These states are specified with this variable. If there are, say, 15 occupied states, and one sets this variable to the value "10-18", this means that occupied states from 10 to 15, and unoccupied states from 16 to 18 will be considered.

This variable is a string in list form, i.e. expressions such as "1,2-5,8-15" are valid. You should include a non-zero number of unoccupied states and a non-zero number of occupied states.

Name CasidaKSEnergyWindow
Section Linear Response::Casida
Type float

An alternative to CasidaKohnShamStates for specifying which occupied-unoccupied transitions will be used: all those whose eigenvalue differences are less than this number will be included. If a value less than 0 is supplied, this criterion will not be used.

Name CasidaMomentumTransfer
Section Linear Response::Casida
Type block
Default 0

Momentum-transfer vector for the calculation of the dynamic structure factor. When this variable is set, the transition rates are determined using an exponential operator instead of the normal dipole one.

Name CasidaParallelEigensolver
Section Linear Response::Casida
Type integer

Choose library to use for solving the parallel eigenproblem of the Casida problem. This options is only relevant if a distributed matrix is used (CasidaDistributedMatrix=true). By default, elpa is chosen if available.

Options:

• casida_elpa:
  Use ELPA library as parallel eigensolver
  
• casida_scalapack:
  Use Scalapack as parallel eigensolver
  

Name CasidaPrintExcitations
Section Linear Response::Casida
Type string
Default write all

Specifies which excitations are written at the end of the calculation.

This variable is a string in list form, i.e. expressions such as "1,2-5,8-15" are valid.

Name CasidaQuadratureOrder
Section Linear Response::Casida
Type integer
Default 5

Only applies if CasidaMomentumTransfer is nonzero. Directionally averaged dynamic structure factor is calculated by averaging over the results from a set of $\vec{q}$-vectors. The vectors are generated using Gauss-Legendre quadrature scheme [see e.g. K. Atkinson, J. Austral. Math. Soc. 23, 332 (1982)], and this variable determines the order of the scheme.

Name CasidaSpectrumBroadening
Section Utilities::oct-casida_spectrum
Type float
Default 0.005 Ha

Width of the Lorentzian used to broaden the excitations.

Name CasidaSpectrumEnergyStep
Section Utilities::oct-casida_spectrum
Type float
Default 0.001 Ha

Sampling rate for the spectrum.

Name CasidaSpectrumMaxEnergy
Section Utilities::oct-casida_spectrum
Type float
Default 1.0 Ha

The broadening is done for energies smaller than CasidaSpectrumMaxEnergy.

Name CasidaSpectrumMinEnergy
Section Utilities::oct-casida_spectrum
Type float
Default 0.0

The broadening is done for energies greater than CasidaSpectrumMinEnergy.

Name CasidaSpectrumRotationMatrix
Section Utilities::oct-casida_spectrum
Type block
Default identity

Supply a rotation matrix to apply to the transition dipoles in generating the spectrum. The rotated atomic structure will also be output. Size of matrix must be Dimensions.

Name CasidaTheoryLevel
Section Linear Response::Casida
Type flag
Default eps_diff + petersilka + lrtddft_casida

Choose which electron-hole matrix-based theory levels to use in calculating excitation energies. More than one may be used to take advantage of the significant commonality between the calculations. variational and lrttdft_casida are not usable with complex wavefunctions. Note the restart data saved by each theory level is compatible with all the others.

Options:

• eps_diff:
  Difference of eigenvalues, i.e. independent-particle approximation.
  
• petersilka:
  The Petersilka approximation uses only elements of the Tamm-Dancoff matrix between degenerate transitions (if no degeneracy, this is just the diagonal elements). Also called the "single-pole" approximation. This is acceptable if there is little mixing between single-particle transitions. Ref: M Petersilka, UJ Gossmann, and EKU Gross, Phys. Rev. Lett. 76, 1212 (1996); T Grabo, M Petersilka,and EKU Gross, Theochem 501-502 353 (2000).
  
• tamm_dancoff:
  The Tamm-Dancoff approximation uses only occupied-unoccupied transitions and not unoccupied-occupied transitions. Ref: S Hirata and M Head-Gordon, Chem. Phys. Lett. 314, 291 (1999).
  
• variational:
  Second-order constrained variational theory CV(2)-DFT. Only applies to real wavefunctions. Ref: T Ziegler, M Seth, M Krykunov, J Autschbach, and F Wang, J. Chem. Phys. 130, 154102 (2009).
  
• lrtddft_casida:
  The full Casida method. Only applies to real wavefunctions. Ref: C Jamorski, ME Casida, and DR Salahub, J. Chem. Phys. 104, 5134 (1996) and ME Casida, "Time-dependent density functional response theory for molecules," in Recent Advances in Density Functional Methods, edited by DE Chong, vol. 1 of Recent Advances in Computational Chemistry, pp. 155-192 (World Scientific, Singapore, 1995).
  

Name CasidaTransitionDensities
Section Linear Response::Casida
Type string
Default write none

Specifies which transition densities are to be calculated and written down. The transition density for the many-body state n will be written to a file called rho_0n prefixed by the theory level. Format is set by OutputFormat.

This variable is a string in list form, i.e. expressions such as "1,2-5,8-15" are valid.

Name CasidaWeightThreshold
Section Linear Response::Casida
Type float
Default -1.

Specifies the threshold value for which the individual excitations are printed. i.e. juste-h pairs with weight larger than this threshold will be printed.

If a negative value (default) is set, all coefficients will be printed. For many case, a 0.01 value is a valid option.

Name CasidaWriteDistributedMatrix
Section Linear Response::Casida
Type logical
Default false

Set to true to write out the full distributed Casida matrix to a file using MPI-IO.

Name CGAdditionalTerms
Section SCF::Eigensolver
Type logical
Default no

Used by the cg solver only. Add additional terms during the line minimization, see PTA92, eq. 5.31ff. These terms can improve convergence for some systems, but they are quite costly. If you experience convergence problems, you might try out this option. This feature is still experimental.

Name CGDirection
Section SCF::Eigensolver
Type integer

Used by the cg solver only. The conjugate direction is updated using a certain coefficient to the previous direction. This coeffiction can be computed in different ways. The default is to use Fletcher-Reeves (FR), an alternative is Polak-Ribiere (PR).

Options:

• fletcher:
  The coefficient for Fletcher-Reeves consists of the current norm of the steepest descent vector divided by that of the previous iteration.
  
• polak:
  For the Polak-Ribiere scheme, a product of the current with the previous steepest descent vector is subtracted in the nominator.
  

Name CGEnergyChangeThreshold
Section SCF::Eigensolver
Type float
Default 0.1

Used by the cg solver only. For each band, the CG iterations are stopped when the change in energy is smaller than the change in the first iteration multiplied by this factor. This limits the number of CG iterations for each band, while still showing good convergence for the SCF cycle. The criterion is discussed in Sec. V.B.6 of Payne et al. (1992), Rev. Mod. Phys. 64, 4. The default value is 0.1, which is usually a good choice for LDA and GGA potentials. If you are solving the OEP equation, you might want to set this value to 1e-3 or smaller. In general, smaller values might help if you experience convergence problems. For very small convergence tolerances, choose 0 to disable this criterion.

Name CGOrthogonalizeAll
Section SCF::Eigensolver
Type logical
Default no

Used by the cg solver only. During the cg iterations, the current band can be orthogonalized against all other bands or only against the lower bands. Orthogonalizing against all other bands can improve convergence properties, whereas orthogonalizing against lower bands needs less operations. Moreover, orthogonalizing against all bands can make converging the highest band or unoccupied bands more difficult.

Name ChebyshevFilterBoundMixing
Section SCF::Eigensolver
Type float
Default 0.5

In the first application of the filter, for the first SCF step, the initial lower bound estimate is defined as a linear combination of the smallest and largest eigenvalues of the Hamiltonian. The bound mixing determines the proportion of linear mixing, beta: $b_{lower} = beta min{\lambda} + (\beta - 1) max{\lambda}$ of the smallest and largest eigenvalues.

Name ChebyshevFilterDegree
Section SCF::Eigensolver
Type integer
Default 25

Used by the Chebyshev filter only. The degree of the Chebyshev polynomial used to dampen the interval of eigenstates one is not interested in. If used in conjunction with "OptimizeChebyshevFilterDegree", which is the default, "ChebyshevFilterDegree" defines the the maximum Chebyshev polynomial degree Octopus will consider when determining an approximate, optimal degree.

If not used in conjunction with "OptimizeChebyshevFilterDegree", this defines the polynomial degree used for all SCF steps. The larger the degree, the larger the separation between the subspaces, which will reduce the number of SCF iterations required to reach convergence. However, ChebyshevFilterDegree also directly correlates with the number of matrix-vector products performed on the Hamiltonian per SCF step, and so larger values result in slower SCF cycles. A value in the range 8 <= ChebyshevFilterDegree <= 20 is reasonable.

Name ChebyshevFilterLanczosOrder
Section SCF::Eigensolver
Type integer
Default 5

Used by the Chebyshev filter only. The number of Lanczos iterations used to construct the tridiagonal matrix, from which the upper bound of H is estimated. A value in the range 4 <= ChebyshevFilterLanczosOrder <= 10 is reasonable. Values greater than 10 will raise an assertion.

Name ChebyshevFilterNIter
Section SCF::Eigensolver
Type integer
Default 5

The max number of iterations in the first SCF step of the Chebyshev solver. In practice this does not need to exceed 10, as the eigenstates will vary alot between the first and second SCF steps.

Name CheckPointsMediumFromFile
Section Maxwell::Medium
Type logical
Default no

Whether to re-calculate the points map by artificially shrinking the coordinate system by a factor of 0.99 to check if the points inside the medium surface are properly detected. This works for only one medium surface which is centered in the origin of the coordinate system.

Name ConductivityFromForces
Section Utilities::oct-conductivity_spectrum
Type logical
Default no

(Experimental) If enabled, Octopus will attempt to calculate the conductivity from the forces instead of the current.

Name ConductivitySpectrumTimeStepFactor
Section Utilities::oct-conductivity_spectrum
Type integer
Default 1

In the calculation of the conductivity, it is not necessary to read the velocity at every time step. This variable controls the integer factor between the simulation time step and the time step used to calculate the conductivity.

Name ConvAbsDens
Section SCF::Convergence
Type float
Default 0.0

Absolute convergence of the density:

$\varepsilon = \int {\rm d}^3r \left| \rho^{out}(\bf r) -\rho^{inp}(\bf r) \right|$.

A zero value (the default) means do not use this criterion.

If this criterion is used, the SCF loop will only stop once it is fulfilled for two consecutive iterations.

Name ConvAbsEv
Section SCF::Convergence
Type float
Default 0.0

Absolute convergence of the sum of the eigenvalues:

$ \varepsilon = \left| \sum_{j=1}^{N_{occ}} \varepsilon_j^{out} - \sum_{j=1}^{N_{occ}} \varepsilon_j^{inp} \right| $

A zero value (the default) means do not use this criterion.

If this criterion is used, the SCF loop will only stop once it is fulfilled for two consecutive iterations.

Name ConvEigenError
Section SCF::Convergence
Type logical
Default false

If true, the calculation will not be considered converged unless all states have individual errors less than EigensolverTolerance.

If this criterion is used, the SCF loop will only stop once it is fulfilled for two consecutive iterations.

Name ConvEnergy
Section SCF::Convergence
Type float
Default 0.0

Stop the SCF when the magnitude of change in energy during at one SCF iteration is smaller than this value.

If this criterion is used, the SCF loop will only stop once it is fulfilled for two consecutive iterations.

Name ConvertEnd
Section Utilities::oct-convert
Type integer
Default 1

The last number of the filename or folder.

Name ConvertEnergyMax
Section Utilities::oct-convert
Type float
Default w_max

Maximum energy to output from Fourier transform.

Name ConvertEnergyMin
Section Utilities::oct-convert
Type float
Default 0.0

Minimum energy to output from Fourier transform.

Name ConvertEnergyStep
Section Utilities::oct-convert
Type float
Default $2\; \backslash pi\; /\; T$, where $T$ is the total propagation time

Energy step to output from Fourier transform. Sampling rate for the Fourier transform. If you supply a number equal or smaller than zero, then the sampling rate will be $2 \pi / T$, where $T$ is the total propagation time.

Name ConvertFilename
Section Utilities::oct-convert
Type string
Default “density”

Input filename. The original filename which is going to be converted in the format specified in OutputFormat. It is going to convert various files, it should only contain the beginning of the name. For instance, in the case of the restart files, it should be one space ’ ‘.

Name ConvertFolder
Section Utilities::oct-convert
Type string

The folder name where the input files are. The default is td. if ConvertIterateFolder = true, otherwise restart.

Name ConvertFTMethod
Section Utilities::oct-convert
Type integer
Default FAST_FOURIER

Describes the method used to perform the Fourier Transform

Options:

• fast_fourier:
  Uses Fast Fourier Transform as implemented in the external library.
  
• standard_fourier:
  Uses polinomial approach to the computation of discrete Fourier Transform. It uses the same variable described in how to obtain spectrum from a time-propagation calculation.
  

Name ConvertHow
Section Utilities::oct-convert
Type integer
Default convert_format

Select how the mesh function will be converted.

Options:

• format:
  The format of the mesh function will be convert from the binary file.obf. The format of the output function is set by OutputHow variable.
  
• fourier_transform:
  A fourier transform of the mesh function will be computed. It requieres that ConvertStart and ConvertEnd have to be set.
  
• operation:
  Convert utility will generate a new mesh function constructed by linear combination of scalar function of different mesh functions,
  

Name ConvertIterateFolder
Section Utilities::oct-convert
Type logical
Default true

This variable decides if a folder is going to be iterated or the filename is going to be iterated.

Name ConvertOutputFilename
Section Utilities::oct-convert
Type string
Default “density”

Output filename. The name of the file in which the converted mesh function will be written in the format specified in OutputFormat.

Name ConvertOutputFolder
Section Utilities::oct-convert
Type string

The folder name where the output files will be write. The default is convert.

Name ConvertReadSize
Section Utilities::oct-convert
Type integer
Default mesh%np

How many points are read at once. For the parallel run this has not been yet tested, so it should be one. For the serial run, a number of 100-1000 will speed-up the execution time by this factor.

Name ConvertScalarOperation
Section Utilities::oct-convert
Type block

This variable is used to generate a new mesh function as a linear combination different mesh function having the same mesh. Each row defines an operation for for a single mesh function. The format of the block is the following:
‘variable name’ | ‘folder’ | ‘file’ | ‘operation’

Name ConvertStart
Section Utilities::oct-convert
Type integer

The starting number of the filename or folder. Default is 0 if ConvertIterateFolder = true, otherwise 1.

Name ConvertStep
Section Utilities::oct-convert
Type integer
Default 1

The padding between the filenames or folder.

Name ConvertSubtract
Section Utilities::oct-convert
Type logical
Default false

Decides if a reference file is going to be subtracted.

Name ConvertSubtractFilename
Section Utilities::oct-convert
Type string
Default density

Input filename. The file which is going to subtracted to rest of the files.

Name ConvertSubtractFolder
Section Utilities::oct-convert
Type string
Default .

The folder name which is going to be subtracted.

Name ConvRelDens
Section SCF::Convergence
Type float
Default 1e-6

Relative convergence of the density:

$\varepsilon = \frac{1}{N} \mathrm{ConvAbsDens}$.

N is the total number of electrons in the problem. A zero value means do not use this criterion.

If you reduce this value, you should also reduce EigensolverTolerance to a value of roughly 1/10 of ConvRelDens to avoid convergence problems.

If this criterion is used, the SCF loop will only stop once it is fulfilled for two consecutive iterations.

Name ConvRelEv
Section SCF::Convergence
Type float
Default 0.0

Relative convergence of the sum of the eigenvalues:

$\varepsilon = \frac{ \left| \sum_{j=1}^{N_{occ}} ( \varepsilon_j^{out} - \varepsilon_j^{inp} ) \right|} {\left| \sum_{j=1}^{N_{occ}} \varepsilon_j^{out} \right|} $

If this criterion is used, the SCF loop will only stop once it is fulfilled for two consecutive iterations.

Name Coordinates
Section System::Coordinates
Type block

If XYZCoordinates, PDBCoordinates, and XSFCoordinates were not found, Octopus tries to read the coordinates for the atoms from the block Coordinates. The format is quite straightforward:

%Coordinates
  ‘C’ | -0.56415 | 0.0 | 0.0 | no
  ‘O’ |  0.56415 | 0.0 | 0.0 | no
%

The first line defines a carbon atom at coordinates (-0.56415, 0.0, 0.0), that is not allowed to move during dynamical simulations. The second line has a similar meaning. This block obviously defines a carbon monoxide molecule, if the input units are eV_Angstrom. The number of coordinates for each species must be equal to the dimension of your space (generally 3). Note that in this way it is possible to fix some of the atoms (this is not possible when specifying the coordinates through a PDBCoordinates or XYZCoordinates file). The last column is optional, and the default is yes. It is always possible to fix all atoms using the MoveIons directive.

Name CurrentDensity
Section Hamiltonian
Type integer
Default gradient_corrected

This variable selects the method used to calculate the current density. For the moment this variable is for development purposes and users should not need to use it.

Options:

• gradient:
  The calculation of current is done using the gradient operator. (Experimental)
  
• gradient_corrected:
  The calculation of current is done using the gradient operator with additional corrections for the total current from non-local operators.
  
• hamiltonian:
  The current density is obtained from the commutator of the Hamiltonian with the position operator. (Experimental)
  

Name CurrentDensityFactor
Section Maxwell
Type float
Default 1.0

Fictitous factor to modify the current density coming from partner systems. Note: This factor does not affect the external current density prescribed by the UserDefinedMaxwellExternalCurrent block.

Name CurrentThroughPlane
Section Output
Type block

The code can calculate current traversing a user-defined portion of a plane, as specified by this block. A small plain-text file current-flow will be written containing this information. Only available for 1D, 2D, or 3D. In the format below, origin is a point in the plane. u and v are the (dimensionless) vectors defining the plane; they will be normalized. spacing is the fineness of the mesh on the plane. Integers nu and mu are the length and width of the portion of the plane, in units of spacing. Thus, the grid points included in the plane are x_ij = origin + ispacingu + jspacingv, for nu <= i <= mu and nv <= j <= mv. Analogously, in the 2D case, the current flow is calculated through a line; in the 1D case, the current flow is calculated through a point. Note that the spacing can differ from the one used in the main calculation; an interpolation will be performed.

Example (3D):

%CurrentThroughPlane
   0.0 | 0.0 | 0.0 # origin
   0.0 | 1.0 | 0.0 # u
   0.0 | 0.0 | 1.0 # v
   0.2 # spacing
   0 | 50 # nu | mu
   -50 | 50 # nv | mv
%

Example (2D):

%CurrentThroughPlane
   0.0 | 0.0 # origin
   1.0 | 0.0 # u
   0.2 # spacing
   0 | 50 # nu | mu
%

Example (1D):

%CurrentThroughPlane
   0.0 # origin
%

Name CurvGygiA
Section Mesh::Curvilinear::Gygi
Type float
Default 0.5

The grid spacing is reduced locally around each atom, and the reduction is given by 1/(1+A), where A is specified by this variable. So, if A=1/2 (the default), the grid spacing is reduced to two thirds = 1/(1+1/2). [This is the $A_{\alpha}$ variable in Eq. 2 of F. Gygi and G. Galli, Phys. Rev. B 52, R2229 (1995)]. It must be larger than zero.

Name CurvGygiAlpha
Section Mesh::Curvilinear::Gygi
Type float
Default 2.0 a.u.

This number determines the region over which the grid is enhanced (range of enhancement of the resolution). That is, the grid is enhanced on a sphere around each atom, whose radius is given by this variable. [This is the $a_{\alpha}$ variable in Eq. 2 of F. Gygi and G. Galli, Phys. Rev. B 52, R2229 (1995)]. It must be larger than zero.

Name CurvGygiBeta
Section Mesh::Curvilinear::Gygi
Type float
Default 4.0 a.u.

This number determines the distance over which Euclidean coordinates are recovered. [This is the $b_{\alpha}$ variable in Eq. 2 of F. Gygi and G. Galli, Phys. Rev. B 52, R2229 (1995)]. It must be larger than zero.

Name CurvMethod
Section Mesh::Curvilinear
Type integer
Default curv_uniform

The relevant functions in octopus are represented on a mesh in real space. This mesh may be an evenly spaced regular rectangular grid (standard mode), or else an adaptive or curvilinear grid. We have implemented three kinds of adaptive meshes, although only one is currently working, the one invented by F. Gygi (curv_gygi). The code will stop if any of the other two is invoked. All are experimental with domain parallelization.

Options:

• curv_affine:
  Regular, uniform rectangular grid.
  
• curv_gygi:
  The deformation of the grid is done according to the scheme described by F. Gygi [F. Gygi and G. Galli, Phys. Rev. B 52, R2229 (1995)].
  
• curv_briggs:
  The deformation of the grid is done according to the scheme described by Briggs [E.L. Briggs, D.J. Sullivan, and J. Bernholc, Phys. Rev. B 54 14362 (1996)] (NOT WORKING).
  
• curv_modine:
  The deformation of the grid is done according to the scheme described by Modine [N.A. Modine, G. Zumbach and E. Kaxiras, Phys. Rev. B 55, 10289 (1997)] (NOT WORKING).
  

Name CurvModineJBar
Section Mesh::Curvilinear::Modine
Type float
Default 1/2

Increase in density of points is inverse of this parameter. See N. A. Modine, G. Zumbach, and E. Kaxiras, Phys. Rev. B 55, 10289-10301 (1997).

Name CurvModineJlocal
Section Mesh::Curvilinear::Modine
Type float
Default 0.25

Local refinement around the atoms. Must be between 0 and 1. See N. A. Modine, G. Zumbach, and E. Kaxiras, Phys. Rev. B 55, 10289-10301 (1997).

Name CurvModineJrange
Section Mesh::Curvilinear::Modine
Type float
Default 2 b

Local refinement range (a length). See N. A. Modine, G. Zumbach, and E. Kaxiras, Phys. Rev. B 55, 10289-10301 (1997).

Name CurvModineXBar
Section Mesh::Curvilinear::Modine
Type float
Default 1/3

Size of central flat region (in units of Lsize). Must be between 0 and 1. See N. A. Modine, G. Zumbach, and E. Kaxiras, Phys. Rev. B 55, 10289-10301 (1997).