Exx keywords
Exact exchange parameters
Exx.beta
Mixing parameter beta. In HSE-like functionals, the exchange function is defined as beta E_x^{HF,SR}(omega_{HF}) + (1-beta) E_x^{PBE,SR}(omega_{PBE}) + E_x^{PBE,LR}(omega_{PBE}). If Exx.beta is unset or empty, the default value is used (i.e. 0.25 for HSE06).
type: scalar
default: 0.25
example: Exx.beta = 0.33333
Exx.Gcutoff
Cutoff for the planewave expansion of the atomic orbital products. The higher this value, the more accurate the results, but also the higher the computational expenses. It is crucial to verify convergence in Exx.Gcutoff in hybrid calculations.
type: scalar
default: 4
example: Exx.Gcutoff = 4.0
Exx.dmDistCut
The density matrix (DM) elements will be set to zero if the distance of two atoms is larger than dmDistCut. Thus DM becomes sparser when dmDistCut is shorter and the computation speed increases. The default is 25, but you can try 5-15 at your own risk. The acceleration is usually noticeable if the k-sampling (Exx.qgridn) is quite large (e.g. > [5 5 5]) and/or the unit cell is larger than Exx.dmDistCut itself.
type: scalar
default: 25
example: Exx.dmDistCut = 10
Exx.eta
Equivalent to Exx.SchwarzEta. The Exx matrix elements violating the Schwarz criterion by more than Exx.SchwarzEta will be ignored. The higher this value, the lower the computational expenses, but also less accurate the results. Value larger than 1e-4 is not recommanded.
type: scalar
default: 1e-06
example: Exx.eta = 1e-6
Exx.omegaHF
Screening parameter omega_{HF}. In HSE-like functionals, the exchange function is defined as beta E_x^{HF,SR}(omega_{HF}) + (1-beta) E_x^{PBE,SR}(omega_{PBE}) + E_x^{PBE,LR}(omega_{PBE}). If Exx.omegaHF is unset or empty, the default value is used (i.e. 0.11 for HSE06).
type: scalar
default: 0.11
example: Exx.omegaHF = 0.11
Exx.omegaPBE
Screening parameter omega_{PBE}. In HSE-like functionals, the exchange function is defined as beta E_x^{HF,SR}(omega_{HF}) + (1-beta) E_x^{PBE,SR}(omega_{PBE}) + E_x^{PBE,LR}(omega_{PBE}). If Exx.omegaPBE is unset or empty, the default value is used (i.e. 0.11 for HSE06).
type: scalar
default: 0.11
example: Exx.omegaPBE = 0.11
Exx.SchwarzEta
The Exx matrix elements violating the Schwarz criterion by more than Exx.SchwarzEta will be ignored. The higher this value, the lower the computational expenses, but also less accurate the results. Values larger than 1e-4 are not recommanded. If it is not set, it will take the value of Exx.eta.
type: scalar
default: 1e-06
example: Exx.SchwarzEta = 1e-6
Exx.blockSize
If the system is large, ex: more than 200 atoms, sparsity plays a role. The Exx matrix is divided into a group of submatrices with size (Exx.blockSize*number of LCAO basis). With this division, the memory-consumption is reduced and the speed might be accelerated since some submatrices are super sparse. When your system is small, set it equal or larger than basis number to maximize the speed. But if your system is large, keep it to default value is good. Suggest 5~10 times bytes memory higher than blockSize*(number of LCAO basis)*16.
type: scalar
default: 256
example: Exx.blockSize = 256
Exx.qgridn
Exx.qgridn is a [1x3] array determining the q-sampling (reciprocal space grid) of the Hartree-Fock exchange term. It is analogous to kpoint.gridn. The grid is forced to be uniform and Gamma-centered. It is equal to kpoint.gridn by default, but it may usually be choosen coarser (not finer however) than the k-grid to reduce the computational cost. This is useful for HSE-like functional computations thanks to the short-range property of the Coulomb potential. q_i*L_i >= 15 is recommneded for all HSE calculations where q_i the grid number and L_i the length of the cell along the ith-axis.
type: array
default: equal to kpoint.grid
size: [1,3]
example: Exx.qgridn = [4 4 4]
Exx.DMinput
The file path that saves LCAO density matrix. Must be assigned by the user. Users can use the PBE density-matrix as initial guess for HSE06 calculations
type: string
example: Exx.DMinput = './results/c_lcao_hse_scf'
Exx.VFinput
The file path that saves LCAO exact exchange matrix. Needed for band/dos calculations
type: string
default: rho.in
example: Exx.VFinput = './results/c_lcao_hse_scf'
Exx.highGcorr
Perform correction to the electron-repulsion integral for G vectors with energies higher than Gcutoff.
type: scalar
default: true
allowed: true,false
example: Exx.highGcorr = true
Exx.doPostExx
Upon convergence, RESCU recalculated the displaced form of the Fock potential matrix without BvK zone folding. This can provide more accurate results when k-sampling is coarse, but sufficient.
type: scalar
allowed: true,false
example: Exx.doPostExx = true