Notes on Options

Note

The options referred to in the Theoretical Methods: SCF to FCI section below and indexed in Keywords by Module are placed in set blocks as described in Job Control Keywords, not as arguments to a Python function (like energy()).

Note

All PSI4 keyword names and values are insensitive to case, both those that are placed in set blocks and as Python function arguments. The few exceptions are documented for the database() function, where case structure must match the database file.

Note

Boolean options can be specified by yes, on, true, or 1 for affirmative and no, off, false, or 0 for negative, all insensitive to case.

Note

Certain convergence and tolerance keywords, of type double (real numbers), may be specified using either a real number or an integer; and integer X is then treated as the number of converged decimal digits required. For example, to request as energy converged to \(10^{-6} E_h\), the user may set the e_convergence keyword to 0.000001, 1.0e-6, or 6.

Alternate Implementations

Depending on the reference (RHF, UHF, ROHF) and the integral treatment (conventional CONV, density-fitted DF, and Cholesky-decomposed CD), computational methods are sometimes implemented by multiple coders or even multiple times. PSI4 transparently selects the most efficient implementation, so one generally needn’t consult this table. However, to understand the details of what combinations are accessible or what alternate implementations are available, read on.

Below, “Y” means method available in module, “D” means module is default for that method, and “” means method not available. HF, DFT, and MP2 default to density-fitted integrals, while all higher methods default to conventional integrals. Therefore, for a closed-shell molecule:

  • runs MP2 with default DF with default implementation DFMP2

    1
    energy('mp2')
    
  • runs MP2 with CONV with default implementation OCC

    1
    2
    set mp2_type conv
    energy('mp2')
    
  • runs MP2 with default DF with implementation OCC

    1
    2
    set qc_module occ
    energy('mp2')
    
Overlapping capabilities of PSI4. “Y” is available; “D” is default.

name

_

type select [1]

QC_MODULE

REFERENCE

_

energy() gradient()
RHF UHF ROHF RHF UHF ROHF
CV DF CD CV DF CD CV DF CD CV DF CD CV DF CD CV DF CD

mp2

MP2_TYPE

CCENERGY                                    
DETCI Y           Y                      
DFMP2   D [2]     D [2]     D     D              
FNOCC Y                                  
OCC D Y D D Y Y D Y D D Y   D D        

mp3

MP_TYPE

CCENERGY                                    
DETCI Y           Y [3]                      
DFMP2                                    
FNOCC Y                                  
OCC D D D D D D       D D   D D        

mp2.5

MP_TYPE

CCENERGY                                    
DETCI                                    
DFMP2                                    
FNOCC                                    
OCC D D D D D D       D D   D D        

mp4

MP_TYPE

CCENERGY                                    
DETCI Y           Y [3]                      
DFMP2                                    
FNOCC D                                  
OCC                                    

lccd

CC_TYPE

CCENERGY                                    
DETCI                                    
DFMP2                                    
FNOCC D                                  
OCC Y D D D D D       D D   D D        

lccsd, cepa(0)

CC_TYPE

CCENERGY                                    
DETCI                                    
DFMP2                                    
FNOCC D                                  
OCC                                    

ccsd

CC_TYPE

CCENERGY D     D     D     D     D     D    
DETCI                                    
DFMP2                                    
FNOCC Y D D                              
OCC   Y Y               D              

ccsd(t)

CC_TYPE

CCENERGY D     D     D     D     D          
DETCI                                    
DFMP2                                    
FNOCC Y D D                              
OCC   Y Y                              

ccsd(at)

CC_TYPE

CCENERGY D                                  
DETCI                                    
DFMP2                                    
FNOCC                                    
OCC   D D                              

cisd

CI_TYPE

CCENERGY                                    
DETCI Y           D                      
DFMP2                                    
FNOCC D                                  
OCC                                    

adc(2)

MP_TYPE

ADCC Y     D                            
BUILTIN D                                  

Footnotes

[1]Algorithm type selection keyword below. Values to the right: conventional CONV (here abbreviated CV), density-fitted DF, and Cholesky-decomposed CD.
[2](1, 2) Also available for KS reference.
[3](1, 2) Conditions have no default module (computationally inefficient) and can only be accessed by specifying QC_MODULE.