{"id":155,"date":"2022-06-16T16:24:27","date_gmt":"2022-06-16T08:24:27","guid":{"rendered":"https:\/\/www.homechemer.com\/?p=155"},"modified":"2022-06-17T00:11:02","modified_gmt":"2022-06-16T16:11:02","slug":"gaussian-to-q-chem-a-stationary","status":"publish","type":"post","link":"https:\/\/www.homechemer.com\/computchem\/2","title":{"rendered":"Gaussian to Q-Chem: A Stationary"},"content":{"rendered":"\n

Gaussian to Q-Chem: A Stationary<\/strong><\/p>\n\n\n\n

Jiawei Xu and Yunlong Shang
Released: 2022-03-17 \/ Updated: 2022-06-16<\/p>\n\n\n\n

This stationary is aimed to help Gaussian users to get familiar with common input keywords in Q-Chem.
Developers:<\/strong> Jiawei Xu and Yunlong Shang
Acknowledgement:<\/strong> We thank Prof. Haiyan Wei from Nanjing Normal University for her advice, computation resources and support in software.<\/p>\n\n\n\n

Part I. Job Settings<\/strong><\/p>\n\n\n\n

Keywords for Gaussian<\/th>Notes for Gaussian<\/th>Keywords for Q-Chem<\/th>Notes for Q-Chem<\/th><\/tr><\/thead>
–Link1–<\/td>Need one blank line before.<\/td>@@@<\/td><\/td><\/tr>
%Mem=[Memory]<\/td><\/td>Mem_Total N<\/mark>
Mem_Static N<\/mark><\/td>		Default: 8000 MB<\/mark>
Default: 64 MB<\/mark> for AO integrals.<\/td><\/tr>
%Chk=[filename].chk<\/td>Save binary checkpoint file.<\/td>GUI 2<\/mark> or IQMol_FChk True<\/mark><\/td>Save formatted checkpoint file.<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

Part II. Basic Keywords<\/strong><\/p>\n\n\n\n

Keywords for Gaussian<\/th>Notes for Gaussian<\/th>Keywords for Q-Chem<\/th>Notes for Q-Chem<\/th><\/tr><\/thead>
NoSymm<\/td>Do not use symmetry to accelerate and do not reorient molecule to standard orientation.<\/td>(1) Symmetry True\/False<\/mark>
(2) Sym_Ignore True\/False<\/mark>
(3) Sym_Tol N<\/mark>
(4) Symmetry_Decomposition N<\/mark><\/td>		(1) Default: True<\/mark>. Use symmetry in calculation.
(2) Default: True<\/mark>. Decide whether to reorient molecule.
(3) Default: 5<\/mark>. Tolerance for point group: 10-N<\/sup>.
(4) Default: 1<\/mark>. Calculate MO symmetry.<\/td><\/tr>
HF<\/td><\/td>Method HF<\/mark><\/td>Hartree-Fock method.<\/td><\/tr>
[functional name]<\/mark><\/td>Density functional theory.<\/td>(1) Method [functional name]<\/mark>
(2) Exchange [functional name]<\/mark>
(3) Correlation [functional name]<\/mark><\/td>		Density functional theory.
Exchange and correlation enable use of generic definition of functional.<\/td><\/tr>
[basis set name]<\/mark><\/td><\/td>Basis [basis set name]<\/mark><\/td><\/td><\/tr>
Integral=Grid=[grid setting]<\/mark><\/td>Fine<\/mark>: 75,302.
UltraFine<\/mark>: 99,590; Default in G16.
SuperFine<\/mark>: 175,974 (H\/He); 250,974 (Else).<\/td>		XC_Grid N<\/mark><\/td>Default: 2<\/mark> (Fine) for meta-GGAs and B95-, B-97 based; 3<\/mark> (UltraFine) for Minnesota functionals.
Alternative to SuperFine in Gaussian: XC_Grid 000175000974 \/ 000250000974<\/mark><\/td><\/tr>
R<\/mark>\/U<\/mark>[HF or<\/em> functional name]<\/td>If not explicit, restricted shell is default for singlet state and unrestricted for else.<\/td>Unrestricted True\/False<\/mark><\/td>Same default with Gaussian.<\/td><\/tr>
RO<\/mark>[HF or<\/em> functional name]<\/td>Restricted open-shell Hartree-Fock (ROHF) or Kohn-Sham (ROKS).<\/td>Method HF<\/mark> or<\/em> [functional name]<\/mark>
Unrestricted False<\/mark><\/td>		For non-singlet systems only.<\/td><\/tr>
Guess=Read<\/mark><\/td><\/td>SCF_Guess Read<\/mark><\/td><\/td><\/tr>
Geom=AllCheck<\/mark><\/td><\/td>Read<\/mark><\/td>(in $Molecule section)<\/td><\/tr>
Out=wfn<\/td>Read extra input for .wfn filename from end of input file.<\/td>Write_wfn filename<\/mark><\/td><\/td><\/tr>
SCF=Conver=N<\/mark><\/td>Default: 8<\/mark> (Synonym: SCF=Tight)<\/td>SCF_Convergence N<\/mark><\/td>Default value is related to jobtype. (10–N<\/em><\/sup> for RMS and 10-(N<\/em>-2)<\/sup> for density)<\/td><\/tr>
SCF=MaxCycle=N<\/mark><\/td>Default: 128<\/mark><\/td>SCF_Max_Cycles N<\/mark><\/td>Default: 50<\/mark>. The default value may be too small for some systems.<\/td><\/tr>
SCF=VShift=N<\/mark><\/td>Default: 100<\/mark>. Level shift: N<\/em>\/1000 a.u.<\/td>Step_Epsilon N<\/mark><\/td>Default: 10<\/mark>. Level shift: N<\/em>\/100 a.u.<\/td><\/tr>
SP<\/td>Singlet point. (This is default when no job type is specified.)<\/td>JobType Energy<\/mark><\/td>Singlet point. (This is default when no job type is specified.)<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

Part III. Keywords for Specific Job Type<\/strong><\/p>\n\n\n\n

III.1 Optimization and PES Scan<\/strong><\/p>\n\n\n\n

Keywords for Gaussian<\/th>Notes for Gaussian<\/th>Keywords for Q-Chem<\/th>Notes for Q-Chem<\/th><\/tr><\/thead>
Opt<\/td><\/td>JobType Opt<\/mark><\/td><\/td><\/tr>
Opt=TS<\/mark><\/td><\/td>JobType TS<\/mark><\/td><\/td><\/tr>
Opt=ModRedundant<\/mark><\/td>Read extra input after coordinates.<\/td>JobType PES_Scan<\/mark><\/td>(In $Scan section)
Stre [A1] [A2] Start End Increment
Bend [A1] [A2] [A3] Start End Increment
Tors [A1] [A2] [A3] [A4] Start End Increment<\/td><\/tr>
Scan<\/td><\/td>JobType PES_Scan<\/mark>
(in $Scan section) Frozen_Scan True\/False<\/mark><\/td>		Default: False<\/mark> (do not freeze).<\/td><\/tr>
Opt=[initial Hessian]<\/mark><\/td>(1) CalcFC<\/mark>: calculate Hessian matrix at the first step of geometry optimization.
(2) ReadFC<\/mark>: read initial Hessian from .oldchk or .chk file.<\/td>		Geom_Opt_Hessian [initial Hessian]<\/mark><\/td>(1) Default: Diagonal<\/mark>. This is a special method in Q-Chem for cheap Hessian matrix at the first step.
(2) Read<\/mark>: read pre-calculated Hessian.<\/td><\/tr>
Opt=[coordinates]<\/mark><\/td>(1) Cartesian<\/mark>
(2) Z-Matrix<\/mark><\/td>		Geom_Opt_Coords [coordinates]<\/mark><\/td>(1) Default: -1<\/mark>. Switch to Cartesian if internal coordinates fails.
(2) 0<\/mark>: Cartesian.
(3) 1<\/mark>: Z-matrix<\/td><\/tr>
Opt=[convergence]<\/mark><\/td>(1) Loose<\/mark>
(2) Tight<\/mark>
(3) VeryTight<\/mark><\/td>		Geom_Opt_Tol_Gradient N<\/mark>
Geom_Opt_Tol_Displacement N<\/mark>
Geom_Opt_Tol_Energy N<\/mark><\/td>		(1) Default: 300<\/mark> (Tolerance: N<\/em>\u00d710-6<\/sup> a.u.)
(2) Default: 1200 <\/mark>(Tolerance: N<\/em>\u00d710-6<\/sup> a.u.)
(3) Default: 100<\/mark> (Tolerance: N<\/em>\u00d710-8<\/sup> a.u.)<\/td><\/tr>
Opt=MaxCycles=N<\/mark><\/td><\/td>Geom_Opt_Max_Cycles N<\/mark><\/td>Default: 50<\/mark>. The default value may be too small for some systems.<\/td><\/tr>
Opt=MaxStep=N<\/mark><\/td>Max step size: N<\/em>\u00d710-2<\/sup> Bohr.<\/td>Geom_Opt_DMax N<\/mark><\/td>Default: 300<\/mark>. Max step size: N<\/em>\u00d710-3<\/sup> Bohr.<\/td><\/tr>
NoSymm<\/td><\/td>Geom_Opt_SymFlag True\/False<\/mark><\/td>Default: True<\/mark>. Control whether to track symmetry only<\/em> in geometry optimization.<\/td><\/tr>
Opt=GDIIS<\/mark><\/td><\/td>Geom_Opt_Max_DIIS N<\/mark><\/td>Default: 0<\/mark> (Do not use DIIS.).<\/td><\/tr>
Freq=NFreq=N<\/mark><\/td>This is only available for ONIOM.<\/td>Geom_Opt_ChaRac True\/False<\/mark><\/td>Default: False<\/mark>. Better to be set as True<\/mark> in TS optimization.<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

III.2 Excited State Methods<\/strong><\/p>\n\n\n\n

Keywords for Gaussian<\/th>Notes for Gaussian<\/th>Keywords for Q-Chem<\/th>Notes for Q-Chem<\/th><\/tr><\/thead>
CIS<\/td><\/td>Method HF<\/mark><\/td>When CIS_N_Roots<\/em> is set to non-zero.<\/td><\/tr>
TD<\/td><\/td>Method [functional name]<\/mark><\/td>When CIS_N_Roots<\/em> is set to non-zero.<\/td><\/tr>
CIS\/TD(NStates=N<\/mark>)<\/td>Default: 3<\/mark>.<\/td>CIS_N_Roots N<\/mark><\/td>No default so must be specified.<\/td><\/tr>
CIS\/TD(Root=N<\/mark>)<\/td>Default: 1<\/mark>.<\/td>CIS_State_Deriv N<\/mark><\/td>No default so must be specified.<\/td><\/tr>
CIS\/TD(Singlet<\/mark>)<\/td>This is default.
Note that singlet<\/em> and triplet<\/em> only work for closed-shell systems or other spin-adapted methods.<\/td>		CIS_Singlets True\/False<\/mark><\/td>Default: True<\/mark><\/td><\/tr>
CIS\/TD(Triplet<\/mark>)<\/td><\/td>CIS_Triplets True\/False<\/mark><\/td>Default: True<\/mark><\/td><\/tr>
CIS\/TD(NStates=N<\/mark>,50-50<\/mark>)<\/td>Search for N<\/mark> singlet states and N<\/mark> triplet states.<\/td><\/td>There is no such keyword in Q-Chem.<\/td><\/tr>
Density=Current<\/td><\/td>CIS_Relaxed_Density True\/False<\/mark><\/td>Default: False<\/mark>.<\/td><\/tr>
<\/td><\/td>Max_CIS_Cycles N<\/mark><\/td>Default: 30<\/mark>. The default value may be too small for some systems.<\/td><\/tr>
<\/td><\/td>CIS_Convergence N<\/mark><\/td>Default: 6 (Threshold for convergence 10–N<\/em><\/sup>)<\/td><\/tr>
<\/td>Default: 2\u00d7NStates<\/mark><\/td>CIS_Subspace N<\/mark><\/td>Default: As many as required.<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

Part IV. Special Functions in Q-Chem<\/strong><\/p>\n\n\n\n

IV.1 Spin-Flip TDDFT<\/strong><\/p>\n\n\n\n

Keywords<\/th>Notes<\/th><\/tr><\/thead>
Spin_Flip True\/False<\/mark><\/td>Default: False<\/mark>.
SF-TDDFT in Q-Chem is flip-down framework. Although available theoretically, flip-up framework is not<\/em> currently supported in Q-Chem.
ROKS ground state is not<\/em> supported in Q-Chem. (It is available in GAMESS.)<\/td><\/tr>
CIS_S2_Thresh N<\/mark><\/td>Default: 120<\/mark> (Threshold for <S2<\/sup>> of singlet state: N<\/em>\/100)<\/td><\/tr>
SASF_RPA True\/False<\/mark><\/td>Default: False<\/mark>.
To perform spin-adapted SF-TDDFT. Although reference state is open-shell, excited states remain eigenfunctions of S2<\/sup> operator so no spin contamination.
Analytical derivative is not<\/em> currently available for SA-SF-TDDFT.<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

IV.2 Minimum Energy Crossing Point Search<\/strong><\/p>\n\n\n\n

Keywords<\/th>Notes<\/th><\/tr><\/thead>
JobType Opt<\/mark>
MECP_Opt True<\/mark><\/td>		Perform MECP search.
Since this is a optimization job, options for JobType <\/em>Opt<\/mark> can also influence MECP search.<\/td><\/tr>
MECP_Methods [method]<\/mark><\/td>Default: Branching_Plane<\/mark> (Branching plane updating method, BPUPD).
Direct<\/mark>: Calculate gradient difference vector and derivative coupling vectors directly. This needs to calculate non-adiabatic coupling, which can be time-consuming.
Penalty_Function<\/mark>: Use penalty function method to accelerate convergence when geometry is far from MECP structure.<\/td><\/tr>
MECP_State1 [[Spin]<\/mark>,[State_Deriv]<\/mark>]
MECP_State2 [[Spin]<\/mark>,[State_Deriv]<\/mark>]<\/td>		Specify two states for MECP search.
For example, MECP_State1 <\/em>[0<\/mark>,1<\/mark>] involves S1<\/sub> state in MECP search. To involve ground state, set State_Deriv<\/mark><\/em> to 0<\/mark>.<\/td><\/tr><\/tbody><\/table><\/figure>\n\n\n\n

<\/p>\n","protected":false},"excerpt":{"rendered":"

Gaussian to Q-Chem: A Sta …<\/p>\n","protected":false},"author":9,"featured_media":0,"comment_status":"closed","ping_status":"closed","sticky":false,"template":"","format":"standard","meta":{"spay_email":"","footnotes":""},"categories":[5],"tags":[],"class_list":["post-155","post","type-post","status-publish","format-standard","hentry","category-computchem"],"jetpack_featured_media_url":"","_links":{"self":[{"href":"https:\/\/www.homechemer.com\/index.php?rest_route=\/wp\/v2\/posts\/155","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/www.homechemer.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/www.homechemer.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/www.homechemer.com\/index.php?rest_route=\/wp\/v2\/users\/9"}],"replies":[{"embeddable":true,"href":"https:\/\/www.homechemer.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=155"}],"version-history":[{"count":19,"href":"https:\/\/www.homechemer.com\/index.php?rest_route=\/wp\/v2\/posts\/155\/revisions"}],"predecessor-version":[{"id":201,"href":"https:\/\/www.homechemer.com\/index.php?rest_route=\/wp\/v2\/posts\/155\/revisions\/201"}],"wp:attachment":[{"href":"https:\/\/www.homechemer.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=155"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/www.homechemer.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=155"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/www.homechemer.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=155"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}