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Keywords

The specification of each keyword is given below. The list does not include all the keywords in OpenMX, and those keywords will be explained in each corresponding section.

File name

System.CurrrentDir
The output directory of output files is specified by this keyword. The default is './'.

System.Name
The file name of output files is specified by this keyword.

DATA.PATH
The path to the VPS and PAO directories can be specified in your input file by the following keyword: 

    DATA.PATH   ../DFT_DATA13    # default=../DFT_DATA13
Both the absolute and relative specifications are available. The default is '../DFT_DATA13'.

level.of.stdout
The amount of the standard output during the calculation is controlled by the keyword 'level.of.stdout'. In case of 'level.of.stdout=0', minimum information. In case of 'level.of.stdout=1', standard information. In case of 'level.of.stdout=2', additional information together with the minimum output information. 'level.of.stdout=3' is for developers. The default is 1.

level.of.fileout
The amount of information output to the files is controlled by the keyword 'level.of.fileout'. In case of 'level.of.fileout=0', minimum information (no Gaussian cube and grid files). In case of 'level.of.fileout=1', standard output. In case of 'level.of.fileout=2', additional information together with the standard output. The default is 1.

Definition of Atomic Species

Species.Number
The number of atomic species in the system is specified by the keyword 'Species.Number'.

Definition.of.Atomic.Species
Please specify atomic species by giving both the file name of pseudo-atomic basis orbitals and pseudopotentials which must be existing in the directories 'DFT_DATA13/PAO' and 'DFT_DATA13/VPS', respectively. For example, they are specified as follows: 
   <Definition.of.Atomic.Species
    H   H5.0-s1>1p1>1      H_CA13
    C   C5.0-s1>1p1>1      C_CA13
   Definition.of.Atomic.Species>
The beginning of the description must be '$<$Definition.of.Atomic.Species', and the last of the description must be 'Definition.of.Atomic.Species$>$'. In the first column, you can give any name to specify the atomic species. The name is used in the specification of atomic coordinates by
'Atoms.SpeciesAndCoordinates'. In the second column, the file name of the pseudo-atomic basis orbitals without the file extension and the number of primitive orbitals and contracted orbitals are given. Here we introduce an abbreviation of the basis orbital we used as H4.0-s1$>$1p1$>$1, where H4.0 indicates the file name of the pseudo-atomic basis orbitals without the file extension which must exist in the directory 'DFT_DATA13/PAO', s1$>$1 means that one optimized orbitals are constructed from one primitive orbitals for the s-orbital, which means no contraction. Also, in case of s1$>$1, corresponding to no contraction, you can use a simple notation 's1' instead of 's1$>$1'. Thus, 'H4.0-s1p1' is equivalent to 'H4.0-s1$>$1p1$>$1'. In the third column, the file name for the pseudopotentials without the file extension is given. Also the file must exist in the directory 'DFT_DATA13/VPS'. It can be possible to assign as the different atomic species for the same atomic element by specifying the different basis orbitals and pseudopotentials. For example, you can define the atomic species as follows: 
   <Definition.of.Atomic.Species
    H1   H5.0-s1p1         H_CA13
    H2   H5.0-s2p2d1       H_CA13
    C1   C5.0-s2p2         C_CA13
    C2   C5.0-s2p2d2       C_CA13
   Definition.of.Atomic.Species>
The flexible definition may be useful for the decrease of computational efforts, in which only high level basis functions are used for atoms belonging to the essential part which determines the electric properties in the system, and lower level basis functions are used for atoms in the other inert parts.

Atoms

Atoms.Number
The total number of atoms in the system is specified by the keyword 'Atoms.Number'.

Atoms.SpeciesAndCoordinates.Unit
The unit of the atomic coordinates is specified by the keyword 'Atoms.SpeciesAndCoordinates.Unit'. Please specify 'Ang' when you use the unit of Angstrom, and 'AU' when the unit of atomic unit. The fractional coordinate is also available by 'FRAC'. Then, please specify the coordinates spanned by ${\bf a}$, ${\bf b}$, and ${\bf c}$-axes given in 'Atoms.UnitVectors'. In the fractional coordinates, the coordinates can range from -0.5 to 0.5, and the coordinates beyond its range will be automatically adjusted after the input file is read.

Atoms.SpeciesAndCoordinates
The atomic coordinates and the number of spin charge are given by the keyword
'Atoms.SpeciesAndCoordinates' as follows: 
   <Atoms.SpeciesAndCoordinates
     1   C      0.000000    0.000000    0.000000     2.0  2.0 
     2   H     -0.889981   -0.629312    0.000000     0.5  0.5
     3   H      0.000000    0.629312   -0.889981     0.5  0.5
     4   H      0.000000    0.629312    0.889981     0.5  0.5
     5   H      0.889981   -0.629312    0.000000     0.5  0.5
   Atoms.SpeciesAndCoordinates>
The beginning of the description must be '$<$Atoms.SpeciesAndCoordinates', and the last of the description must be 'Atoms.SpeciesAndCoordinates$>$'. The first column is a sequential serial number for identifying atoms. The second column is given to specify the atomic species which must be given in the first column of the specification of the keyword 'Definition.of.Atomic.Species' in advance. In the third, fourth, and fifth columns, x-, y-, and z-coordinates are given. When 'FRAC' is chosen for the keyword 'Atoms.SpeciesAndCoordinates.Unit', the third, fourth, and fifth columns are fractional coordinates spanned by ${\bf a}$, ${\bf b}$, and ${\bf c}$-axes, where the coordinates can range from -0.5 to 0.5, and the coordinates beyond its range will be automatically adjusted after the input file is read. The sixth and seventh columns give the number of initial charges for up and down spin states of each atom, respectively. The sum of up and down charges must be the number of valence electrons for the atomic element. When you calculate spin-polarized systems using 'LSDA-CA' or 'LSDA-PW', you can give the initial spin charges for each atom, which might be those of the ground state, to accelerate the SCF convergence.

Atoms.UnitVectors.Unit
The unit of the vectors for the unit cell is specified by the keyword 'Atoms.UnitVectors.Unit'. Please specify 'Ang' when you use the unit of Angstrom, and 'AU' when the unit of atomic unit.

Atoms.UnitVectors
The vectors, ${\bf a}$, ${\bf b}$, and ${\bf c}$ of the unit cell are given by the keyword 'Atoms.UnitVectors' as follows: 
   <Atoms.UnitVectors                     
     10.0   0.0   0.0  
      0.0  10.0   0.0  
      0.0   0.0  10.0  
   Atoms.UnitVectors>
The beginning of the description must be '$<$Atoms.UnitVectors', and the last of the description must be 'Atoms.UnitVectors$>$'. The first, second, and third rows correspond to the vectors, ${\bf a}$, ${\bf b}$, and ${\bf c}$ of the unit cell, respectively. If the keyword is absent in the cluster calculation, a unit cell is automatically determined so that the isolated system cannot overlap with the image systems in the repeated cells. See also the Section 'Automatic determination of the cell size'.

SCF or Electronic System

scf.XcType
The keyword 'scf.XcType' specifies the exchange-correlation potential. Currently, 'LDA', 'LSDA-CA', 'LSDA-PW', and 'GGA-PBE' are available, where 'LSDA-CA' is the local spin density functional of Ceperley-Alder [2], 'LSDA-PW' is the local spin density functional of Perdew-Wang, in which the gradient of density is set to zero in their GGA formalism [4]. Note: 'LSDA-CA' is faster than 'LSDA-PW'. 'GGA-PBE' is a GGA functional proposed by Perdew et al [5].

scf.SpinPolarization
The keyword 'scf.SpinPolarization' specifies the non-spin polarization or the spin polarization for the electronic structure. If the calculation for the spin polarization is performed, then specify 'ON'. If the calculation for the non-spin polarization is performed, then specify 'OFF'. When you use 'LDA' for the keyword 'scf.XcType', the keyword 'scf.SpinPolarization' must be 'OFF'. In addition to these options, 'NC' is supported for the non-collinear DFT calculation. For this calculation, see also the Section 'Non-collinear DFT'.

scf.partialCoreCorrection
The keyword 'scf.partialCoreCorrection' is a flag for a partial core correction (PCC) in calculations of exchange-correlation energy and potential. 'ON' means that PCC is made, and 'OFF' is none. In any cases, the flag should be 'ON', since pseudopotentials generated with PCC should be used with PCC, and also PCC does not affect the result for pseudopotentials without PCC because of zero PCC charge in this case.

scf.Hubbard.U
In case of the LDA+U or GGA+U calculation, the keyword 'scf.Hubbard.U' should be switched 'ON' (ON$\vert$OFF). The default is 'OFF'.

scf.Hubbard.Occupation
In the LDA+U method, three occupation number operators 'onsite', 'full', and 'dual' are available which can be specified by the keyword 'scf.Hubbard.Occupation'.

Hubbard.U.values
An effective U-value on each orbital of species is defined by the following keyword: 
   <Hubbard.U.values                 #  eV
    Ni  1s 0.0 2s 0.0 1p 0.0 2p 0.0 1d 4.0 2d 0.0
    O   1s 0.0 2s 0.0 1p 0.0 2p 0.0 1d 0.0
   Hubbard.U.values>

The beginning of the description must be '$<$Hubbard.U.values', and the last of the description must be 'Hubbard.U.values$>$'. For all the basis orbitals specified by the 'Definition.of.Atomic.Species', you have to give an effective U-value in the above format. The '1s' and '2s' mean the first and second s-orbital, and the number behind '1s' is the effective U-value (eV) for the first s-orbital. The same rule is applied to p- and d-orbitals.

scf.Constraint.NC.Spin
The keyword 'scf.Constraint.NC.Spin' should be switched 'ON' (ON$\vert$OFF) when the constraint DFT method for the non-collinear spin orientation is performed.

scf.Constraint.NC.Spin.v
The keyword 'scf.Constraint.NC.Spin.v' gives a prefactor (eV) of the penalty functional in the constraint DFT for the non-collinear spin orientation.

scf.ElectronicTemperature
The electronic temperature (K) is given by the keyword 'scf.ElectronicTemperature'. The default is 300 (K).

scf.energycutoff
The keyword 'scf.energycutoff' specifies the cutoff energy which is used in the calculation of matrix elements associated with difference charge Coulomb potential and exchange-correlation potential and the solution of Poisson's equation using fast Fourier transform (FFT). The default is 150 (Ryd).

scf.Ngrid
The keyword 'scf.Ngrid' gives the number of grids to discretize the a-, b-, and c-axes. Although 'scf.energycutoff' is usually used for the discretization, the numbers of grids are specified by 'scf.Ngrid', they are used for the discretization instead of those by 'scf.energycutoff'.

scf.maxIter
The maximum number of SCF iterations is specified by the keyword 'scf.maxIter'. The SCF loop is terminated at the number specified by 'scf.maxIter' even if a convergence criterion is not satisfied. The default is 40.

scf.EigenvalueSolver
The solution method for the eigenvalue problem is specified by the keyword 'scf.EigenvalueSolver'. An O($N$) divide-conquer method 'DC', an O($N$) Krylov subspace method 'Krylov', a numerically exact low-order scaling method 'ON2', the cluster calculation 'Cluster', and the band calculation 'Band' are available.

scf.Kgrid
When you specify the band calculation 'Band' for the keyword 'scf.EigenvalueSolver', then you need to give a set of numbers (n1,n2,n3) of grids to discretize the first Brillouin zone in the k-space by the keyword 'scf.Kgrid'. For the reciprocal vectors ${\bf\tilde{a}}$, ${\bf\tilde{b}}$, and ${\bf\tilde{c}}$ in the k-space, please provide a set of numbers (n1,n2,n3) of grids as n1 n2 n3. The k-points in OpenMX are generated by a regular mesh method.

scf.ProExpn.VNA
Switch on the keyword 'scf.ProExpn.VNA' in case that the neutral atom potential VNA is expanded by projector operators [31]. Otherwise turn off. The default is 'ON'. 
       scf.ProExpn.VNA      ON      # ON|OFF, default = ON

In case that 'scf.ProExpn.VNA=OFF', the matrix elements for the VNA potential are evaluated by using the regular mesh in real space.

scf.Mixing.Type
A mixing method of the electron density (or the density matrix) to generate an input electron density at the next SCF step is specified by keyword 'scf.Mixing.Type'. A simple mixing method ('Simple'), 'GR-Pulay' method (Guaranteed-Reduction Pulay method) [41], 'RMM-DIIS' method [42], 'Kerker' method [43], 'RMM-DIISK' method [42] and 'RMM-DIISH' method [42] are available. The simple mixing method used here is modified to accelerate the convergence, referring to a convergence history. When 'GR-Pulay', 'RMM-DIIS', 'Kerker', 'RMM-DIISK', or 'RMM-DIISH' is used, the following recipes are helpful to obtain faster convergence of SCF calculations: Among these mixing schemes, the robustest one might be 'RMM-DIISK'.

scf.Init.Mixing.Weight
The keyword 'scf.Init.Mixing.Weight' gives the initial mixing weight used by the simple mixing, the GR-Pulay, the RMM-DIIS, the Kerker, the RMM-DIISK, and the RMM-DIISH methods. The valid range is $0<$scf.Init.Mixing.Weight$<1$. The default is 0.3.

scf.Min.Mixing.Weight
The keyword 'scf.Min.Mixing.Weight' gives the lower limit of a mixing weight in the simple and Kerker mixing methods. The default is 0.001.

scf.Max.Mixing.Weight
The keyword 'scf.Max.Mixing.Weight' gives the upper limit of a mixing weight in the simple and Kerker mixing methods. The default is 0.4.

scf.Kerker.factor
The keyword gives a Kerker factor which is used in the Kerker and RMM-DIISK mixing methods. If the keyword is not given, a proper value is automatically determined. For further details, see the Section 'SCF convergence'.

scf.Mixing.History
In the GR-Pulay method [41], the RMM-DIIS method [42], the Kerker method [43], the RMM-DIISK method [42], and the RMM-DIISH method [42], the input electron density (Hamiltonian) at the next SCF step is estimated based on the output electron densities (Hamiltonian) in the several previous SCF steps. The keyword 'scf.Mixing.History' specifies the number of previous SCF steps which are used in the estimation. For example, if 'scf.Mixing.History' is specified to be 3, and when the SCF step is 6th, the electron densities at 5, 4, and 3 SCF steps are taken into account. Around 30 is a better choice.

scf.Mixing.StartPulay
The SCF step which starts the GR-Pulay, the RMM-DIIS, the Kerker, the RMM-DIISK, and the RMM-DIISH methods is specified by the keyword 'scf.Mixing.StartPulay'. The SCF steps before starting these Pulay-type methods are then performed by the simple or Kerker mixing methods. The default is 6.

scf.Mixing.EveryPulay
The residual vectors in the Pulay-type mixing methods tend to become linearly dependent each other as the mixing steps accumulate, and the linear dependence among the residual vectors makes the convergence difficult. A way of avoiding the linear dependence is to do the Pulay-type mixing occasionally during the Kerker mixing. With this prescription, you can specify the frequency using the keyword 'scf.Mixing.EveryPulay'. For example, in case of 'scf.Mixing.EveryPulay=5', the Pulay-mixing is made at every five SCF iterations, while the Kerker mixing is used at the other steps. 'scf.Mixing.EveryPulay=1' corresponds to the conventional Pulay-type mixing. It is noted that the keyword 'scf.Mixing.EveryPulay' is supported for only 'RMM-DIISK', and the default value is 1.

scf.criterion
The keyword 'scf.criterion' specifies a convergence criterion (Hartree) for the SCF calculation. The SCF iteration is ended when a condition, dUele$<$scf.criterion, is satisfied, where dUele is defined as the absolute deviation between the eigenvalue energy at the current and previous SCF steps. The default is 1.0e-6 (Hartree).

scf.Electric.Field
give The keyword 'scf.Electric.Field' gives the strength of a uniform external electric field given by a sawtooth waveform. For example, when an electric field of 1.0 GV/m (10$^9$ V/m) is applied along the a-axis, specify in your input file as follows: 
     scf.Electric.Field   1.0 0.0 0.0   # default=0.0 0.0 0.0 (GV/m)
The sign of electric field is taken as that applied to electrons. The default is 0.0 0.0 0.0.

scf.system.charge
The keyword 'scf.system.charge' gives the amount of the electron and hole dopings. The plus and minus signs correspond to hole and electron dopings, respectively. The default is 0.

scf.SpinOrbit.Coupling
When the spin-orbit coupling is included, the keyword should be 'ON', otherwise please set to 'OFF'. In case of the inclusion of the spin-orbit coupling, you have to use j-dependent pseudopotentials. See also the Section 'Relativistic effects' as for the j-dependent pseudopotentials.

1D FFT

1DFFT.EnergyCutoff
The keyword '1DFFT.EnergyCutoff' gives the energy range to tabulate the Fourier transformed radial functions of pseudo-atomic orbitals and of the projectors for non-local potentials. The default is 3600 (Ryd).

1DFFT.NumGridK
The keyword '1DFFT.NumGridK' gives the the number of radial grids in the k-space. The values of the Fourier transformation for radial functions of pseudo-atomic orbitals and of the projectors for non-local potentials are tabulated on the grids, ranging from zero to 1DFFT.EnergyCutoff, as a function of radial axis in the k-space. The default is 900.

1DFFT.NumGridR
The keyword '1DFFT.NumGridR' gives the the number of radial grids in real space which is used in the numerical grid integrations of the Fourier transformation for radial functions of pseudo-atomic orbitals and of the projectors for non-local potentials. The default is 900.

Orbital Optimization

orbitalOpt.Method
The keyword 'orbitalOpt.Method' specifies a method for the orbital optimization. When the orbital optimization is not performed, then choose 'OFF'. When the orbital optimization is performed, the following two options are available: 'atoms' in which basis orbitals on each atom are fully optimized, 'species' in which basis orbitals on each species are optimized. In 'atoms', the radial functions of basis orbitals are optimized with a constraint that the radial wave function $R$ is independent on the magnetic quantum number, which guarantees the rotational invariance of the total energy. However, the optimized orbital on all the atoms can be different from each other. In the 'species', basis orbitals in atoms with the same species name, that you define in 'Definition.of.Atomic.Species', are optimized as the same orbitals. If you want to assign the same orbitals to atoms with almost the same chemical environment, and optimize these orbitals, this scheme is useful.

orbitalOpt.scf.maxIter
The maximum number of SCF iterations in the orbital optimization is specified by the keyword 'orbitalOpt.scf.maxIter'.

orbitalOpt.Opt.maxIter
The maximum number of iterations for the orbital optimization is specified by the keyword 'orbitalOpt.Opt.maxIter'. The iteration loop for the orbital optimization is terminated at the number specified by 'orbitalOpt.Opt.maxIter' even if a convergence criterion is not satisfied.

orbitalOpt.Opt.Method
Two schemes for the optimization of orbitals are available: 'EF' which is an eigenvector following method, 'DIIS' which is the direct inversion method in iterative subspace. The algorithms are basically the same as for the geometry optimization. Either 'EF' or 'DIIS' is chosen by the keyword 'orbitalOpt.Opt.Method'.

orbitalOpt.StartPulay
The quasi Newton method 'EF' and 'DIIS' starts from the optimization step specified by the keyword 'orbitalOpt.StartPulay'.

orbitalOpt.HistoryPulay
The keyword 'orbitalOpt.HistoryPulay' specifies the number of previous steps to estimate the next input contraction coefficients used in the quasi Newton method 'EF' and 'DIIS'.

orbitalOpt.SD.step
The orbital optimization at optimization steps before moving to the quasi Newton method 'EF' or 'DIIS' is performed by the steepest decent method. The prefactor used in the steepest decent method is specified by the keyword 'orbitalOpt.SD.step'. In most cases, 'orbitalOpt.SD.step' of 0.001 can be a good prefactor.

orbitalOpt.criterion
The keyword 'orbitalOpt.criterion' specifies a convergence criterion ((Hartree/Borg)$^2$) for the orbital optimization. The iterations loop is finished when a condition, Norm of derivatives$<$orbitalOpt.criterion, is satisfied.

CntOrb.fileout
If you want to output the optimized radial orbitals to files, then the keyword 'CntOrb.fileout' must be 'ON'.

Num.CntOrb.Atoms
The keyword 'Num.CntOrb.Atoms' gives the number of atoms whose optimized radial orbitals are output to files.

Atoms.Cont.Orbitals
The keyword 'Atoms.Cont.Orbitals' specifies the atom number, which is given by the first column in the specification of the keyword 'Atoms.SpeciesAndCoordinates' for the output of optimized orbitals as follows: 
    <Atoms.Cont.Orbitals
     1
     2
    Atoms.Cont.Orbitals>
The beginning of the description must be '$<$Atoms.Cont.Orbitals', and the last of the description must be 'Atoms.Cont.Orbitals$>$'. The number of lines should be consistent with the number specified in the keyword 'Atoms.Cont.Orbitals'. For example, the name of files are C_1.pao and H_2.pao, where the symbol corresponds to that given by the first column in the specification of the keyword 'Definition.of.Atomic.Species' and the number after the symbol means that of the first column in the specification of the keyword 'Atoms.SpeciesAndCoordinates'. These output files 'C_1.pao' and 'H_2.pao' can be an input data for pseudo-atomic orbitals as is.

SCF Order-N

orderN.HoppingRanges
The keyword 'orderN.HoppingRanges' defines the radius of a sphere which is centered on each atom. The physically truncated cluster for each atom is constructed by picking up atoms inside the sphere with the radius in the DC and Krylov subspace O($N$) methods.

orderN.KrylovH.order
The dimension of the Krylov subspace of Hamiltonian in each truncated cluster is given by the 'orderN.KrylovH.order'.

orderN.KrylovS.order
In case of 'orderN.Exact.Inverse.S=off', the inverse is approximated by a Krylov subspace method for the inverse, where the dimension of the Krylov subspace of overlap matrix in each truncated cluster is given by the keyword 'orderN.KrylovS.order'. The default value is 'orderN.KrylovH.order'$\times 4$.

orderN.Exact.Inverse.S
In case of 'orderN.Exact.Inverse.S=on', the inverse of overlap matrix for each truncated cluster is exactly evaluated. Otherwise, see the keyword 'orderN.KrylovS.order'. The default is 'on' (on$\vert$off).

orderN.Recalc.Buffer
In case of 'orderN.Recalc.Buffer=on', the buffer matrix is recalculated at every SCF step. Otherwise, the buffer matrix is calculated at the first SCF step, and fixed at subsequent SCF steps. The default is 'on' (on$\vert$off).

orderN.Expand.Core
In case of 'orderN.Expand.Core=on', the core region is defined by atoms within a sphere with radius of $1.2\times r_{\rm min}$, where $r_{\rm min}$ is the distance between the central atom and the nearest atom. The core region defines a set of vectors used for the first step in the generation of the Krylov subspace for each truncated cluster. In case of 'orderN.Expand.Core=off', the central atom is considered as the core region. The default is 'on' (on$\vert$off).

MD or Geometry Optimization

MD.Type
Please specify the type of the molecular dynamics calculation or the geometry optimization. Currently, NO MD (Nomd), MD with the NVE ensemble (NVE), MD with the NVT ensemble by a velocity scaling scheme (NVT_VS)[19], MD with the NVT ensemble by a Nose-Hoover scheme (NVT_NH) [20], MD with multi-heat bath (NVT_VS2 or NVT_VS4), the geometry optimization by the steepest decent (SD) method (Opt), DIIS optimization method (DIIS), the eigenvector following (EF) method (EF) [47], and the rational function (RF) method (RF) [48] are available. For the details, see the Sections 'Geometry optimization' and 'Molecular dynamics'.

MD.Fixed.XYZ
In the geometry optimization and the molecular dynamics simulations, it is possible to separately fix the x-, y-, and z-coordinates of the atomic position to the initial position in your input file by the following keyword: 
    <MD.Fixed.XYZ
      1  1 1 1
      2  1 0 0
    MD.Fixed.XYZ>

The example is for a system consisting of two atoms. If you have N atoms, then you have to provide N rows in this specification. The 1st column is the same sequential number to specify atom as in the specification of the keyword 'Atoms.SpeciesAndCoordinates'. The 2nd, 3rd, and 4th columns are flags for the x-, y-, and z-coordinates, respectively. '1' means that the coordinate is fixed, and '0' relaxed. In the above example, the x-, y-, and z-coordinates of the atom '1' are fixed, only the x-coordinate of the atom '2' is fixed. The default setting is that all the coordinates are relaxed. The fixing of atomic positions are valid all the geometry optimizers and molecular dynamics schemes.

MD.maxIter
The keyword 'MD.maxIter' gives the number of MD iterations.

MD.TimeStep
The keyword 'MD.TimeStep' gives the time step (fs).

MD.Opt.criterion
When any of the geometry optimizers is chosen for the keyword 'MD.Type', then the keyword 'MD.Opt.criterion' specifies a convergence criterion (Hartree/Bohr). The geometry optimization is finished when a condition, the maximum force on atom is smaller than 'MD.Opt.criterion', is satisfied.

MD.Opt.DIIS.History
The keyword 'MD.Opt.DIIS.History' gives the number of previous steps to estimate the optimized structure used in the geometry optimization by 'DIIS', 'EF', and 'RF'. The default value is 3.

MD.Opt.StartDIIS
The geometry optimization step at which 'DIIS', 'EF', or 'RF' starts is specified by the keyword 'MD.Opt.StartDIIS'. The geometry optimization steps before starting the DIIS-type method is performed by the steepest decent method. The default value is 5.

MD.TempControl
The keyword specifies temperature for atomic motion in MD of the NVT ensembles. In 'NVT_VS', the temperature for nuclear motion can be controlled by 
   <MD.TempControl
     3
     100   2  1000.0  0.0  
     400  10   700.0  0.4  
     700  40   500.0  0.7  
   MD.TempControl>
The beginning of the description must be '$<$MD.TempControl', and the last of the description must be 'MD.TempControl$>$'. The first number '3' gives the number of the following lines to control the temperature. In this case, you can see that there are three lines. Following the number '3', in the consecutive lines the first column means MD steps and the second column gives the interval of MD steps that the velocity scaling is made. For the above example, a velocity scaling is performed at every two MD steps until 100 MD steps, at every 10 MD steps from 100 to 400 MD steps, and at every 40 MD steps from 400 to 700 MD steps. The third and fourth columns give a given temperature (K) and a scaling parameter $\alpha$ in the interval. For further details see the Section 'Molecular dynamics'. On the other hand, in NVT_NH, the temperature for nuclear motion can be controlled by 
   <MD.TempControl
     4
     1    1000.0
     100  1000.0
     400   700.0
     700   600.0
   MD.TempControl>
The beginning of the description must be '$<$MD.TempControl', and the last of the description must be 'MD.TempControl$>$'. The first number '4' gives the number of the following lines to control the temperature. In this case you can see that there are four lines. Following the number '4', in the consecutive lines the first and second columns give the MD steps and a given temperature for nuclear motion. The temperature between the MD steps explicitly specified by the keyword is given by linear interpolation.

NH.Mass.HeatBath
In 'NVT_NH', a mass of heat bath is given by the keyword. The default mass is 20, where we use the unified atomic mass unit that the principal isotope of carbon atom is 12.0.

MD.Init.Velocity
For molecular dynamics simulations, it is possible to provide the initial velocity of each atom by the following keyword: 
  <MD.Init.Velocity
   1    3000.000  0.0  0.0
   2   -3000.000  0.0  0.0
  MD.Init.Velocity>
The example is for a system consisting of two atoms. If you have N atoms, then you have to provide N rows in this specification. The 1st column is the same sequential number to specify atom as in the specification of the keyword 'Atoms.SpeciesAndCoordinates'. The 2nd, 3rd, and 4th columns are x-, y-, and z-components of the velocity of each atom. The unit of the velocity is m/s. The keyword 'MD.Init.Velocity' is compatible with the keyword 'MD.Fixed.XYZ'.
Band dispersion

Band.dispersion
When you evaluate the band dispersion, please specify 'ON' for the keyword 'Band.dispersion'.

Band.KPath.UnitCell
The keyword 'Band.KPath.UnitCell' gives unit vectors, which are used in the calculation of the band dispersion, as follows: 
   <Band.KPath.UnitCell
    3.56 0.0 0.0
    0.0 3.56 0.0
    0.0 0.0 3.56
   Band.KPath.UnitCell>
The beginning of the description must be '$<$Band.KPath.UnitCell', and the last of the description must be 'Band.KPath.UnitCell$>$'. If 'Band.KPath.UnitCell' exists, the reciprocal lattice vectors for the calculation of the band dispersion are calculated by the unit vectors specified in 'Band.KPath.UnitCell'. If 'Band.KPath.UnitCell' is not found, the reciprocal lattice vectors, which are calculated by the unit vectors specified in 'Atoms.UnitVectors', is employed for the calculation of the band dispersion. In case of fcc, bcc, base centered cubic, and trigonal cells, the reciprocal lattice vectors for the calculation of the band dispersion should be specified using the keyword 'Band.KPath.UnitCell' based on the consuetude in the band calculations.

Band.Nkpath
The keyword 'Band.Nkpath' gives the number of paths for the band dispersion.

Band.kpath
The keyword 'Band.kpath' specifies the paths of the band dispersion as follows: 
    <Band.kpath                
      15  0.0 0.0 0.0   1.0 0.0 0.0   g X
      15  1.0 0.0 0.0   1.0 0.5 0.0   X W
      15  1.0 0.5 0.0   0.5 0.5 0.5   W L
      15  0.5 0.5 0.5   0.0 0.0 0.0   L g
      15  0.0 0.0 0.0   1.0 1.0 0.0   g X 
    Band.kpath>
The beginning of the description must be '$<$Band.kpath', and the last of the description must be 'Band.kpath$>$'. The number of lines should be consistent with 'Band.Nkpath'. The first column is the number of grids at which eigenvalues are evaluated on the path. The following (n1, n2, n3) and (n1', n2', n3'), spanned by the reciprocal lattice vectors, specifies the starting and ending k-points of the path in the first Brillouin zone. If 'Band.KPath.UnitCell' is found, the reciprocal lattice vectors for the calculation of the band dispersion are calculated by the unit vectors specified in 'Band.KPath.UnitCell'. If 'Band.KPath.UnitCell' is not found, the reciprocal lattice vectors, which are calculated by the unit vectors specified in 'Atoms.UnitVectors' is employed for the calculation of the band dispersion. The final two alphabets give the name of the starting and ending k-points of the path.

Restarting

scf.restart
If you want to restart the SCF calculation using a previous file 'System.Name_rst/*' which should be generated in the previous calculation, then set the keyword 'scf.restart' to 'ON'.

Output of molecular orbitals (MOs)

MO.fileout
If you want to output molecular orbitals (MOs) to files, then set the keyword 'MO.fileout' to 'ON'.

num.HOMOs
The keyword 'num.HOMOs' gives the number of the highest occupied molecular orbitals (HOMOs) that you want to output to files.

num.LUMOs
The keyword 'num.LUMOs' gives the number of the lowest unoccupied molecular orbitals (LUMOs) that you want to output to files.

MO.Nkpoint
When you have specified 'MO.fileout=ON' and 'scf.EigenvalueSolver=Band', the keyword 'MO.Nkpoint' gives the number of the k-points at which you output MOs to files.

MO.kpoint
The keyword 'MO.kpoint' specifies the k-point, at which MOs are evaluated for the output to files, as follows: 
   <MO.kpoint
     0.0  0.0  0.0
   MO.kpoint>
The beginning of the description must be '$<$MO.kpoint', and the last of the description must be 'MO.kpoint$>$'. The k-points are specified by (n1, n2, n3) which is spanned by the reciprocal lattice vectors, where the the reciprocal lattice vectors are determined in the same way as 'Band.kpath'.

DOS and PDOS

Dos.fileout
If you want to evaluate density of states (DOS) and projected partial density of states (PDOS), please set in 'Dos.fileout=ON'.

Dos.Erange
The keyword 'Dos.Erange' determines the energy range for the DOS calculation as 
    Dos.Erange               -10.0  10.0
The first and second values are the lower and upper bounds of the energy range (eV) for the DOS calculation, respectively.

Dos.Kgrid
The keyword, Dos.Kgrid, gives a set of numbers (n1,n2,n3) of grids to discretize the first Brillouin zone in the k-space, which is used in the DOS calculation.

Interface for developers

HS.fileout
If you want to use Kohn-Sham Hamiltonian, overlap, and density matrices, please set in 'HS.fileout=ON'. Then, these data are stored to 'System.Name.scfout' in a binary form, where 'System.Name' is the file name specified by the keyword 'System.Name'. The utilization of these data is illustrated in the Section 'Interface for developers'.

Voronoi charge

Voronoi.charge
If you want to calculate Voronoi charges, then set the keyword 'Voronoi.charge' in 'ON'. The result is found in 'System.Name.out', 'System.Name' is the file name specified by the keyword 'System.Name'.

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2016-04-03