# DFOCC

Performs density-fitted orbital-optimized MPn and CC computations and conventional MPn computations.

## General

### CC_DIIS_MAX_VECS

> Maximum number of vectors used in amplitude DIIS

> - Type: integer
> - Default: 6

### CC_DIIS_MIN_VECS

> Minimum number of vectors used in amplitude DIIS

> - Type: integer
> - Default: 2

### CC_LAMBDA

> Do solve lambda amplitude equations?

> - Type: boolean
> - Default: false

### CC_MAXITER

> Maximum number of iterations to determine the amplitudes

> - Type: integer
> - Default: 50

### CHOLESKY

> Do Cholesky decomposition of the ERI tensor

> - Type: boolean
> - Default: false

### CHOLESKY_TOLERANCE

> tolerance for Cholesky decomposition of the ERI tensor

> - Type: conv double
> - Default: 1.0e-4

### COMPUT_S2

> Do compute \(\langle \hat{S}^2 \rangle\) for DF-OMP2/DF-MP2?

> - Type: boolean
> - Default: false

### CUTOFF

> Cutoff value for numerical procedures

> - Type: integer
> - Default: 8

### DO_DIIS

> Do apply DIIS extrapolation?

> - Type: boolean
> - Default: true

### DO_LEVEL_SHIFT

> Do apply level shifting?

> - Type: boolean
> - Default: true

### DO_SCS

> Do perform spin-component-scaled OMP2 (SCS-OMP2)? In all computation, SCS-OMP2 energy is computed automatically. However, in order to perform geometry optimizations and frequency computations with SCS-OMP2, one needs to set ‘DO_SCS’ to true

> - Type: boolean
> - Default: false

### DO_SOS

> Do perform spin-opposite-scaled OMP2 (SOS-OMP2)? In all computation, SOS-OMP2 energy is computed automatically. However, in order to perform geometry optimizations and frequency computations with SOS-OMP2, one needs to set ‘DO_SOS’ to true

> - Type: boolean
> - Default: false

### E3_SCALE

> CEPA opposite-spin scaling value from SCS-CCSD

> - Type: double
> - Default: 0.25

### EKT_IP

> Do compute ionization potentials based on the extended Koopmans’ theorem?

> - Type: boolean
> - Default: false

### E_CONVERGENCE

> Convergence criterion for energy. See Table Post-SCF Convergence for default convergence criteria for different calculation types.

> - Type: conv double
> - Default: 1e-6

### HESS_TYPE

> Type of the MO Hessian matrix

> - Type: string
> - Possible Values: APPROX_DIAG, APPROX_DIAG_EKT, APPROX_DIAG_HF, HF
> - Default: HF

### INTEGRAL_CUTOFF

> Cutoff value for DF integrals

> - Type: integer
> - Default: 9

### LEVEL_SHIFT

> Level shift to aid convergence

> - Type: double
> - Default: 0.02

### LINEQ_SOLVER

> The solver will be used for simultaneous linear equations.

> - Type: string
> - Possible Values: CDGESV, FLIN, POPLE
> - Default: CDGESV

### MAX_MOGRAD_CONVERGENCE

> Convergence criterion for maximum orbital gradient

> - Type: conv double
> - Default: 1e-3

### MOLDEN_WRITE

> Do write a MOLDEN output file? If so, the filename will end in .molden, and the prefix is determined by WRITER_FILE_LABEL (if set), or else by the name of the output file plus the name of the current molecule.

> - Type: boolean
> - Default: false

### MO_DIIS_NUM_VECS

> Number of vectors used in orbital DIIS

> - Type: integer
> - Default: 6

### MO_MAXITER

> Maximum number of iterations to determine the orbitals

> - Type: integer
> - Default: 50

### MO_STEP_MAX

> Maximum step size in orbital-optimization procedure

> - Type: double
> - Default: 0.5

### MP2_AMP_TYPE

> The algorithm that used to handle mp2 amplitudes. The DIRECT option means compute amplitudes on the fly * whenever they are necessary.

> - Type: string
> - Possible Values: DIRECT, CONV
> - Default: DIRECT

### MP2_OS_SCALE

> MP2 opposite-spin scaling value

> - Type: double
> - Default: 6.0

### MP2_SOS_SCALE

> MP2 Spin-opposite scaling (SOS) value

> - Type: double
> - Default: 1.3

### MP2_SOS_SCALE2

> Spin-opposite scaling (SOS) value for optimized-MP2 orbitals

> - Type: double
> - Default: 1.2

### MP2_SS_SCALE

> MP2 same-spin scaling value

> - Type: double
> - Default: 1.0

### NAT_ORBS

> Do compute natural orbitals?

> - Type: boolean
> - Default: false

### OCC_ORBS_PRINT

> Do print OCC orbital energies?

> - Type: boolean
> - Default: false

### OEPROP

> Do compute one electron properties?

> - Type: boolean
> - Default: false

### OO_SCALE

> OO scaling factor used in MSD

> - Type: double
> - Default: 0.01

### OPT_METHOD

> The orbital optimization algorithm. Presently quasi-Newton-Raphson algorithm available with several Hessian * options.

> - Type: string
> - Possible Values: QNR
> - Default: QNR

### ORB_OPT

> Do optimize the orbitals?

> - Type: boolean
> - Default: true

### ORB_RESP_SOLVER

> The algorithm will be used for solving the orbital-response equations. The LINEQ option create the MO Hessian and solve the simultaneous linear equations with method choosen by the LINEQ_SOLVER option. The PCG option does not create the MO Hessian explicitly, instead it solves the simultaneous equations iteratively with the preconditioned conjugate gradient method.

> - Type: string
> - Possible Values: PCG, LINEQ
> - Default: PCG

### ORTH_TYPE

> The algorithm for orthogonalization of MOs

> - Type: string
> - Possible Values: GS, MGS
> - Default: MGS

### PCG_BETA_TYPE

> CEPA type such as CEPA0, CEPA1 etc. currently we have only CEPA0.

> - Type: string
> - Possible Values: FLETCHER_REEVES, POLAK_RIBIERE
> - Default: FLETCHER_REEVES

### PCG_CONVERGENCE

> Convergence criterion for residual vector of preconditioned conjugate gradient method.

> - Type: conv double
> - Default: 1e-6

### PCG_MAXITER

> Maximum number of preconditioned conjugate gradient iterations.

> - Type: integer
> - Default: 50

### PPL_TYPE

> Type of the CCSD PPL term.

> - Type: string
> - Possible Values: LOW_MEM, HIGH_MEM, CD, AUTO
> - Default: AUTO

### QCHF

> Do perform a QCHF computation?

> - Type: boolean
> - Default: false

### READ_SCF_3INDEX

> Do read 3-index integrals from SCF files?

> - Type: boolean
> - Default: true

### REGULARIZATION

> Do use regularized denominators?

> - Type: boolean
> - Default: false

### REG_PARAM

> Regularization parameter

> - Type: double
> - Default: 0.4

### RMS_MOGRAD_CONVERGENCE

> Convergence criterion for RMS orbital gradient. Default adjusts depending on E_CONVERGENCE

> - Type: conv double
> - Default: 1e-6

### R_CONVERGENCE

> Convergence criterion for amplitudes (residuals).

> - Type: conv double
> - Default: 1e-5

### SCS_TYPE

> Type of the SCS method

> - Type: string
> - Possible Values: SCS, SCSN, SCSVDW, SCSMI
> - Default: SCS

### SOS_TYPE

> Type of the SOS method

> - Type: string
> - Possible Values: SOS, SOSPI
> - Default: SOS

### TRIPLES_IABC_TYPE

> The algorithm to handle (ia|bc) type integrals that used for (T) correction.

> - Type: string
> - Possible Values: INCORE, AUTO, DIRECT, DISK
> - Default: DISK

### WFN_TYPE

> Type of the wavefunction.

> - Type: string
> - Default: DF-OMP2