## Issues and Tips for AIMAll (Version 19.10.12)

**System Requirements for "AIMAll (Version 19.10.12)":**

- Windows XP/Vista/Windows 7/Windows 8/Windows 10, Intel/AMD (x86) processor(s), 32-bit or 64-bit, OpenGL-supporting graphics.

- Mac OS X Tiger/Leopard/Snow Leopard/Lion/Mountain Lion/Mavericks/Yosemite/El Capitan/Sierra, Intel/AMD (x86) processor(s), 32-bit or 64-bit, OpenGL-supporting graphics.

- Linux (GLIBC 2.4 or later), Intel/AMD (x86) processor(s), 32-bit or 64-bit, OpenGL-supporting graphics.

**Some Limitations**

- Wavefunctions are limited to basis sets containing S, P, D, F, G and H Gaussian basis function types. Support for higher angular momentum Gaussian basis functions and Slater basis functions is planned.

- Wavefunctions derived from effective core potential (ECP) calculations must include additional core density function data for the ECP-modeled core electrons. More information can be found here.

- Wavefunctions derived from semi-empirical calculations are currently not supported.

- Conflict catastrophes and other catastrophes in the electron density topology are not fully supported yet. Conflict catastrophes are the most important
since they can be non-isolated. Conflict catastrophes usually involve a weak BCP between an atom and another BCP. The default "Proaim" atomic integration algorithm will not work for
atoms connected by a BCP whose interatomic surface contains another BCP, as occurs in a typical conflict catastrophe. The "Promega" atomic integration algorithm should be used for such atoms. Support for conflict catastrophes using
the "Proaim" atomic integration algorithm is being worked on.

- For post-Hartree-Fock (e.g., MP2, CCSD, CIS, etc.), natural orbital AIM "wavefunction" files the Muller approximation
of the two-electron density matrix (2EDM) in terms of natural orbitals of the one-electron density matrix (1EDM) is
used to calculate 2EDM-dependent atomic properties, i.e., the Vee(A,Mol), Vee(A,A) and Vee(A,A') contributions and the electronic localization
and delocalization properties such as LI(A), DI(A,B), D2(A,B), etc. This is necessary because the 2EDM is not available in AIM wavefunction files.
Better approximations of the 2EDM in terms of the 1EDM are being considered, but ultimately the availability of the actual post-Hartreee-Fock 2EDM in AIM wavefunction files is most desirable.

- For Kohn-Sham DFT (KS-DFT) wavefunctions, only certain DFT models (currently LSDA and B3LYP and M062X and PBE and PBE0) are supported for the calculation of atomic DFT-based exchange-correlation energies and additive IQA atomic energies. For more information, see here.

**Some Tips for Use of AIMAll With Gaussian 03 (g03)**

- Some versions of g03 may produce traditional AIM .wfn files with an inconsistency between the nuclear coordinate orientation and the orientation that the MO coefficients correspond to, i.e., the nuclear coordinates are written in the
input orientation while the written MO coefficients correspond to the Gaussian standard orientation (unless the Gaussian keyword NOSYMM is specified). This issue is
usually caught by AIMQB, which performs a normalization check on traditional AIM .wfn files. To avoid this and other issues with traditional AIM .wfn files, it is strongly recommended to open g03 formatted checkpoint files (.fch or .fchk files) with AIMQB instead and then
use the corresponding .wfx files for all AIMAll calculations. Opening formatted checkpoint files with AIMQB and then using the .wfx files with the AIMAll programs is beneficial in several other ways as well.

- For g03 post-SCF, correlated calculations (e.g., MP2, CCSD, etc.) one must use the Gaussian keywords DENSITY=CURRENT (in addition to OUTPUT=WFN) in order for the necessary "natural orbitals" of the correlated first-order total density
matrix to be written to the traditional AIM .wfn file. Use of DENSITY=CURRENT is also necessary for single-point, post-SCF correlated calculations in order for the
correlated first-order density matrix to be written to the checkpoint file and thus the corresponding formatted checkpoint file potentially used by AIMQB.

- For g03 unrestricted, post-SCF, correlated calculations (e.g., UMP2, UCCSD, etc.) one must use the Gaussian keywords POP=NOAB (in addition to DENSITY=CURRENT and OUTPUT=WFN) in order for the necessary
Alpha and Beta "natural spin orbitals" of the correlated Alpha and Beta first-order density matrices to be written separately to the traditional AIM .wfn file. POP=NOAB is not necessary if one intends to open the formatted checkpoint file with AIMQB and then use the .wfx file for all AIMAll calculations.

- For g03 post-SCF, correlated calculations the SCF energy and SCF virial ratio (-V/T) are always written to the traditional AIM .wfn file instead of the necessary total correlated energy and
correlated virial ratio. To correct the traditional AIM .wfn file written by g03, one must manually change the energy and virial ratio at the bottom of the file
to the correlated values. The correlated virial ratio can be calculated as -(E/T)+1, where E is the total correlated energy and T is the correlated
electronic kinetic energy (search for KE= in the correlated population analysis section of the Gaussian log file). This issue can be avoided by opening
the formatted checkpoint file with AIMQB and then using the .wfx file created by AIMQB for all AIMAll calculations.

- When doing single point calculations with g03 for which a subsequent AIMAll analysis of the corresponding fchk file is planned, it is recommended to use the FORCE keyword so that the energy gradients with respect to nuclear coordinates appear in the fchk file and hence the wfx file.

**Some Tips for Use of AIMAll With Gaussian 09 (g09), Revision B.01 or Later**

*Please note that all of the items in this list are applicable only to Revision B.01 or later of Gaussian 09*.

- Gaussian 09 (g09), Revision B.01 or later
**(Revision D.01 or later is recommended)**includes some important new features that are of interest to AIMAll users.

- Traditional AIM wavefunction files (.wfn files) can be written for basis sets containing G, H and higher angular momentum basis functions.

. - The nuclear coordinate orientation in the .wfn file is always consistent with the orientation that the MO coefficients correspond to.

. - The virial ratio and energy at the end of the .wfn file are consistent with the wavefunction. For example, when the MOs are MP2 natural orbitals then the energy and virial ratio
are the MP2 energy and MP2 virial ratio.

- Extended AIM wavefunction files (.wfx files) can be written. To have g09 write a .wfx file at the end
of the job, use the keywords OUTPUT=WFX (or OUTPUT=WFNX) and specify the desired name of the .wfx file at the end of the input file. For example:

------------------------------------------------------------------

%chk=h2o.chk

#p hf/6-311g(d,p) opt output=wfx

H2O HF/6-311G(d,p)//HF/6-311G(d,p)

0 1

O 0.00000000 0.00000000 -0.11081188

H 0.00000000 -0.78397589 0.44324751

H 0.00000000 0.78397589 0.44324751

h2o.wfx

------------------------------------------------------------------

------------------------------------------------------------------

%chk=h2o_mp2.chk

#p mp2(full)/6-311g(d,p) opt output=wfx density=current

H2O MP2(Full)/6-311G(d,p)//MP2(Full)/6-311G(d,p)

0 1

O 0.00000000 0.00000000 -0.11081188

H 0.00000000 -0.78397589 0.44324751

H 0.00000000 0.78397589 0.44324751

h2o_mp2.wfx

------------------------------------------------------------------

------------------------------------------------------------------

%chk=h2o+_mp2.chk

#p mp2(full)/6-311g(d,p) opt output=wfx density=current pop=noab

H2O+ MP2(Full)/6-311G(d,p)//MP2(Full)/6-311G(d,p)

1 2

O 0.00000000 0.00000000 -0.11081188

H 0.00000000 -0.78397589 0.44324751

H 0.00000000 0.78397589 0.44324751

h2o+_mp2.wfx

------------------------------------------------------------------

------------------------------------------------------------------

%chk=h2o_sp.chk

#p hf/6-311g(d,p) output=wfx force

H2O HF/6-311G(d,p) Single Point (With Forces)

0 1

O 0.00000000 0.00000000 -0.11081188

H 0.00000000 -0.78397589 0.44324751

H 0.00000000 0.78397589 0.44324751

h2o_sp.wfx

------------------------------------------------------------------

------------------------------------------------------------------

%chk=h2o_giao.chk

#p hf/6-311g(d,p) output=(wfx,giaocx) nmr

H2O HF/6-311G(d,p) NMR, GIAO method

0 1

O 0.00000000 0.00000000 -0.11081188

H 0.00000000 -0.78397589 0.44324751

H 0.00000000 0.78397589 0.44324751

h2o_giao.wfx

------------------------------------------------------------------

------------------------------------------------------------------

%chk=h2o_csgt.chk

#p hf/6-311g(d,p) output=(wfx,csgtcx) nmr=csgt

H2O HF/6-311G(d,p) NMR, CSGT method

0 1

O 0.00000000 0.00000000 -0.11081188

H 0.00000000 -0.78397589 0.44324751

H 0.00000000 0.78397589 0.44324751

h2o_csgt.wfx

------------------------------------------------------------------

- On Windows, the .wfx file created by Gaussian 09W will usually be written to the Gaussian scratch directory (e.g., C:\G09W\Scratch). On
other platforms the .wfx will usually be written to the directory of the Gaussian input file.

- When Effective Core Potentials (ECPs) are used, g09 automatically writes core density functions for the ECP-modeled core electrons to the .wfx files. AIMAll
uses these additional core electron density functions together with the usual wavefunction data in order to easily and reliably perform QTAIM analyses
of molecular systems containing heavy atoms whose cores were modeled with ECPs.

- For g09 post-SCF, correlated calculations (e.g., MP2, CCSD, CIS, etc.) one must use the Gaussian keywords DENSITY=CURRENT (in addition to OUTPUT=WFX) in order for the necessary "natural orbitals" of the correlated first-order total density
matrix to be written to the .wfx file. Use of DENSITY=CURRENT is also necessary for single-point, post-SCF correlated calculations in order for the
correlated first-order density matrix to be written to the checkpoint file and thus the corresponding formatted checkpoint file potentially used by AIMQB.

- For g09 unrestricted, post-SCF, correlated calculations (e.g., UMP2, UCCSD, UCIS, etc.) one must use the Gaussian keywords POP=NOAB (in addition to DENSITY=CURRENT and OUTPUT=WFX) in order for the necessary
Alpha and Beta "natural spin orbitals" of the correlated Alpha and Beta first-order density matrices to be written separately to the traditional AIM .wfn file. POP=NOAB is not necessary if one intends to open the formatted checkpoint file with AIMQB and then use the .wfx file for all AIMAll calculations.

- When doing single point calculations with g09 for which a subsequent AIMAll analysis of the corresponding .wfx file or .fchk file is planned, it is recommended to use the FORCE keyword so that the energy gradients with respect to nuclear coordinates
appear in the fchk file and hence the .wfx file.

- The orientation of the Nuclear Cartesian Energy Gradients written to the .wfx files written by g09, Revision B.01 (but not later versions of g09) may be inconsistent with
the orientation corresponding to the Nuclear Cartesian Coordinates and the MO coefficients. When the gradients are significant in magnitude (i.e., non-stationary point geometries), this inconsistency makes the Full Virial Ratio written to the .wfx file incorrect. In the AIMAll .sum and .sumviz result files, this inconsistency makes the
nuclear virial contributions, W(A), to the total atomic energies, E(A), incorrect as well as the energy-gradient-based forces, -GradE(A), and the corrected atomic and corrected total Feynman forces. This issue can be ignored if the gradients are very small (e.g., for tightly optimized equilibrium geometries or transition state geometries) or by users who are uninterested in properties determined by the Nuclear Cartesian Energy Gradients. This issue can be avoided by updating to Gaussian 09, Revision D.01 or later or by using the NOSYMM keyword or by opening
the formatted checkpoint file with AIMQB and then using the .wfx file created by AIMQB for all AIMAll calculations instead. For a g09 ECP calculation, from which the .wfx
file created by g09
**must**be used, the Nuclear Cartesian Cartesian Energy Gradients and Full Virial Ratio from the AIMQB-created .wfx file can be copied to the g09-created .wfx file.

- g09 C.01 may sometimes write invalid .wfx files for post-scf methods (e.g., MP2, CCSD, etc.), invalid because at least some of the natural orbitals and / or their occupancies are incorrect. This issue can be avoided by updating to Gaussian 09, Revision D.01 or later. To workaround this issue one can open the Gaussian formatted checkpoint files (.fch or .fchk files) with AIMQB instead and then use the corresponding .wfx files for all AIMAll calculations.

Copyright © 1997-2019 by Todd A. Keith