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# SAPT

Performs symmetry adapted perturbation theory (SAPT) analysis to quantitatively analyze noncovalent interactions.

## General

### AIO_CPHF

> Do use asynchronous disk I/O in the solution of the CPHF equations? Use may speed up the computation slightly at the cost of spawning an additional thread.

> - Type: boolean
> - Default: false

### AIO_DF_INTS

> Do use asynchronous disk I/O in the formation of the DF integrals? Use may speed up the computation slightly at the cost of spawning an additional thread.

> - Type: boolean
> - Default: false

### BASIS

> Primary basis set, describes the monomer molecular orbitals

> - Type: string
> - Possible Values: basis string
> - Default: No Default

### CCD_E_CONVERGENCE

> E converge value for CCD

> - Type: conv double
> - Default: 1e-8

### CCD_MAXITER

> Max CCD iterations

> - Type: integer
> - Default: 50

### CCD_T_CONVERGENCE

> Convergence tolerance for CCD amplitudes

> - Type: conv double
> - Default: 1e-8

### DENOMINATOR_ALGORITHM

> Denominator algorithm for PT methods. Laplace transformations are slightly more efficient.

> - Type: string
> - Possible Values: LAPLACE, CHOLESKY
> - Default: LAPLACE

### DENOMINATOR_DELTA

> Maximum error allowed (Max error norm in Delta tensor) in the approximate energy denominators employed for most of the and evaluation.

> - Type: double
> - Default: 1.0e-6

### DF_BASIS_ELST

> Auxiliary basis set for SAPT Elst10 and Exch10 density fitting computations, may be important if heavier elements are involved. Defaults to DF_BASIS_SAPT

> - Type: string
> - Possible Values: basis string
> - Default: No Default

### DF_BASIS_SAPT

> Auxiliary basis set for SAPT density fitting computations. Defaults to a RI basis.

> - Type: string
> - Possible Values: basis string
> - Default: No Default

### D_CONVERGENCE

> Convergence criterion for residual of the CPHF coefficients in the SAPT term.

> - Type: conv double
> - Default: 1e-8

### E_CONVERGENCE

> Convergence criterion for energy (change) in the SAPT term during solution of the CPHF equations.

> - Type: conv double
> - Default: 1e-10

### FREEZE_CORE

> The scope of core orbitals to freeze in evaluation of SAPT and terms. Recommended true for all SAPT computations

> - Type: string
> - Possible Values: FALSE, TRUE
> - Default: FALSE

### INTS_TOLERANCE

> Minimum absolute value below which all three-index DF integrals and those contributing to four-index integrals are neglected. The default is conservative, but there isn’t much to be gained from loosening it, especially for higher-order SAPT.

> - Type: conv double
> - Default: 1.0e-12

### MAXITER

> Maxmum number of CPHF iterations

> - Type: integer
> - Default: 50

### MAX_CCD_DIISVECS

> Maximum number of vectors used in CCD-DIIS

> - Type: integer
> - Default: 10

### MIN_CCD_DIISVECS

> Minimumnumber of vectors used in CCD-DIIS

> - Type: integer
> - Default: 4

### NAT_ORBS_T2

> Do use MP2 natural orbital approximations for the block of two-electron integrals in the evaluation of second-order T2 amplitudes? Recommended true for all SAPT computations.

> - Type: boolean
> - Default: false

### NAT_ORBS_T3

> Do natural orbitals to speed up evaluation of the triples contribution to dispersion by truncating the virtual orbital space? Recommended true for all SAPT computations.

> - Type: boolean
> - Default: false

### NAT_ORBS_V4

> Do use MP2 natural orbital approximations for the block of two-electron integrals in the evaluation of CCD T2 amplitudes? Recommended true for all SAPT computations.

> - Type: boolean
> - Default: false

### NO_RESPONSE

> Don’t solve the CPHF equations? Evaluate and instead of their response-including coupterparts. Only turn on this option if the induction energy is not going to be used.

> - Type: boolean
> - Default: false

### OCC_TOLERANCE

> Minimum occupation (eigenvalues of the MP2 OPDM) below which virtual natural orbitals are discarded for in each of the above three truncations

> - Type: conv double
> - Default: 1.0e-6

### PRINT

> The amount of information to print to the output file for the sapt module. For 0, only the header and final results are printed. For 1, (recommended for large calculations) some intermediate quantities are also printed.

> - Type: integer
> - Default: 1

### SAPT_LEVEL

> The level of theory for SAPT

> - Type: string
> - Possible Values: SAPT0, SAPT2, SAPT2+, SAPT2+3
> - Default: SAPT0

### SAPT_MEM_CHECK

> Do force SAPT2 and higher to die if it thinks there isn’t enough memory? Turning this off is ill-advised.

> - Type: boolean
> - Default: true

### SAPT_MEM_SAFETY

> Memory safety

> - Type: double
> - Default: 0.9

### SAPT_OS_SCALE

> The scale factor used for opposite-spin pairs in SCS computations. SS/OS decomposition performed for and terms.

> - Type: double
> - Default: 6.0/5.0

### SAPT_SS_SCALE

> The scale factor used for same-spin pairs in SCS computations. SS/OS decomposition performed for and terms.

> - Type: double
> - Default: 1.0/3.0

## Expert

### DO_CCD_DISP

> Do CCD dispersion correction in SAPT2+, SAPT2+(3) or SAPT2+3?

> - Type: boolean
> - Default: false

### DO_MBPT_DISP

> Do MBPT dispersion correction in SAPT2+, SAPT2+(3) or SAPT2+3, if also doing CCD?

> - Type: boolean
> - Default: true

### DO_THIRD_ORDER

> Do compute third-order corrections?

> - Type: boolean
> - Default: false

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