Adjusted Charge Partitioning and Iterative Adjusted Charge Partitioning

Introduction

Atomic charge schemes, dubbed Adjusted Charge Partitioning (ACP) and Iterative Adjusted Charge Partitioning (I-ACP), are based on a Hirshfeld-like scheme in which weighting factors c_A r^2n–2exp(–α_Ar) are used to partition the valence molecular electron density into atomic components. In the ACP method, both parameters α_A and c_A are pre-defined. In the I-ACP method only α_A is fixed, while c_A is determined iteratively in every calculations.

Built-in parameters are available for 17 main-group elements H, Li to F, Na to Cl, Br, and I. In addition, in the case of the I-ACP method, the α_Ti is available for titanium. Users are free to introduce and to use their own parameters for any element.

The ACP scheme is non-iterative, therefore simple and reliable. The I-ACP scheme is more flexible and equally reliable, but the calculation is slightly more expensive. Both ACP and I-ACP are specifically designed for the resulting atomic charges to accurately reproduce the molecular dipole moment.

The ACP atomic charges can be calculated by the program ACP:
ACP.exe – Windows version
ACP.x – Linux version

Similarly, the program I-ACP serves to calculate the Iterative ACP charges:
I-ACP.exe – Windows version
I-ACP.x – Linux version

Both programs can be downloaded here free of charge

Once you use any results calculated by the ACP or I-ACP programs, you have to include the following citations:
For the ACP program:
1. S.F.Vyboishchikov, ACP program, Girona, 2018
2. A.A.Voityuk, A.J.Stasyuk, S.F.Vyboishchikov, "A simple model for calculating atomic charges in molecules" PCCP, 2018, 20, 23328–23337, DOI: 10.1039/c8cp03764g

For the I-ACP program:
1. S.F.Vyboishchikov, I-ACP program, Girona, 2018
2. S.F.Vyboishchikov, A.A.Voityuk, "Iterative atomic-charge partitioning of valence electron density" J. Comp. Chem., 2019, 40, 875–884, DOI: 10.1002/jcc.25771

Questions related to the ACP and I-ACP methods should be addressed to Alexander Voityuk or Sergei Vyboishchikov. Specific questions about the programs should be addressed to Sergei Vyboishchikov.

Program use

The programs use a Gaussian WFN file produced by the Gaussian option OUTPUT=WFN and is invoked from a Linux or Windows command line interpreter as follows:
For the ACP program:
  ACP.exe file.wfn
      or
  ACP.exe file.wfn [[<option> <parameter> ]   [<option> <parameter> ...  ]]

For the I-ACP program:
  I-ACP.exe file.wfn
      or
  I-ACP.exe file.wfn [[<option> <parameter> ]   [<option> <parameter> ...  ]]

Here file.wfn is a WFN file name.

  Options:
    -r radial_grid
            radial_grid is the number of radial gridpoints per atom (default: 120)

    -a angular_grid
           

angular_grid is the number of angular gridpoints per atom (default: 302)

    -user element_number α_A c_A 
       This option serves to define or re-define α_A and c_A parameters for element element_number. In the case of the I-ACP method, the c_A parameter has to be omitted.

The -user option can be repeated for as many elements as needed.