Only recent updates are shown here. To check full update history since the first release (Nov, 2009), please click: UpdateHistory.txt

- Option 8 is added to post-process menu of main function 4 for most kinds of plane maps. Using this option, chemical bonds can be drawn on the graph as straight lines.
- When using Independent Gradient Model (IGM) anaylsis, if your input file contains wavefunction information, the program will let you choose the kind of the sign(lambda2)rho to be used, the first one is that based on actual electron density, the second one is that based on promolecular density.
- Molden input file produced by NWChem is formally supported. See beginning of Chapter 4 of the manual on how to properly generated it.

- Due to some bugs in EDFlib library, (3,+3) rather than (3,-3) type of AIM critical points are located at nuclear position for some elements when pseudopotential is employed. This problem has been fixed via updating EDFlib.
- When drawing spectra for multiple systems based on .dat file outputted by Grimme's sTDA program, Multiwfn crashes. This problem has been fixed.
- When custom operation involves "+" operator, the program doesn't work. This problem has been fixed, thanks jimkress for reporting.

- A new main function 20 is added, which is a collection of all visual study methods for weak interaction. It can carry out NCI (with/without promolecular approximation), aNCI, DORI, which have already been supported in eariler version, and the newly supported IGM analysis. Correspondingly, the manual is rearranged.
- The Independent Gradient Model (IGM) analysis method proposed in Phys. Chem. Chem. Phys., 19, 17928 (2017) is fully supported and can be performed via subfunction 10 of main function 20. This method can be used to individually visualize intra-fragment and inter-fragment interactions, the contribution of atomic pairs and atoms can be quantified and vividly rendered with help of VMD. In addition, the delta_g function involved in IGM analysis is added as the 22th real space function, its value at bond critical point in weak interaction region is shown to be closely related to interaction strength. See Section 3.22.5 of manual for introduction of IGM method, analysis examples are given in Section 4.20.10.
- Orbital localization analysis module (subfunction 13 of main function 200 in older version) is greatly improved and extended, now it is appeared as main function 19 since it is frequently used. Foster-Boys localization method and Pipek-Mezey localization with Lowdin population are added. In addition, the speed of Pipek-Mezey localization is signifcantly improved compared to older version, now it can be easily used for localizing occupuied orbitals for a system containing about 200 atoms. Moreoever, major character of resulting LMOs are automatically printed so that the users can quickly find the orbitals they are interested in.
- The total/dynamic/nondynamic electron correlation index proposed in Phys. Chem. Chem. Phys., 18, 24015 (2016) have been implemented as subfunction 15 of main function 200. Details can be found in Section 3.200.15 of the manual. .wfn/.wfx/.molden file carrying natural orbitals could be used as input file.
- CCSD(T) wavefunction generated by PSI4 program and arbitrary order of coupled-cluster and CI wavefunctions (including FCI) generated by Kallay's MRCC program can be analyzed by Multiwfn. See Section 4.A.8 of the manual for detail.
- Section 4.18.5 is added to manual, this section describes how to plot transition dipole moment contributed by molecular fragments as arrows in VMD program based on the data outputted by hole-electron analysis module of Multiwfn.
- In main function 1, if input "d", real space function value at a given point can be decomposed into contribution of various orbitals, see Section 3.3 for details. Property decomposition for critical points is also supported in option 7 of topology analysis module.
- MDL molfile (.mol) is supported as input file.
- Electronegativity Equalization Method (EEM) charge now can be easily calculated via suboption 17 of main function 7, see Section 3.9.15 for introduction and Section 4.7.5 for example. Atomic charges of a system composed of hundreds of atoms can be obtained instantly via this method.
- In main function 18, subfunction 8 is added to calculate amount of interfragment charge transfer between any two fragments during electronic excitation, see Section 3.21.8 for detail and 4.18.6 for example.
- Subfunction 22 of main function 100 is significantly extended, now it enables automatically detecting pi orbitals based on localized molecular orbitals for both planar and non-planar systems. This feature makes separate study of sigma and pi electrons quite easy for all kinds of system. See Section 3.100.22 of the manual for detail and Section 4.100.22 for illustrative application.
- Subfunction 9 is added to main function 9, this function can decompose Wiberg bond order in NAO basis as contributions from NAO orbital pairs and NAO shell pairs, and thus makes interactions between atomic orbitals and atomic shells that play key role of covalent bonding can be clearly revealed. See Section 3.11.8 of the manual for details and Section 4.9.4 for example.
- Main function 11 now can plot IR spectrum by using output file of Grimme's xtb program (https://www.chemie.uni-bonn.de/pctc/mulliken-center/software/xtb/xtb) as input file.
- Subfunction 16 is added to main function 200. This function is used to generate natural orbitals, spin natural orbitals and natural spin orbitals based on the density matrix in .fch/.fchk file. See Section 3.200.16 for details.
- Option 5 of subfunction 1 (hole-electron analysis module) of main function 18 now can output atom-atom contribution matrix of transition electric/magnetic dipole moment, and it can be further plotted as colored matrix map. See corresponding description in Section 3.21.1.3.
- Function -2 is added to main function 7 (population analysis module). Using this function the electrostatic interaction energy between two fragments can be calculated based on atomic charges. .chg file should be used as input file since this file records atomic charge information.
- The Strong Covalent Interaction index (SCI) proposed in DOI: 10.1021/acs.jpca.8b00521 is added as the 37th user-defined function, see entry 37 of Section 2.7 for introduction, this function is shown to be very useful for identifying very strong covalent bonds.

- Molden input file produced by Dalton is formally supported
- Mode 10 is added to the interface for setting up grid data, this mode allows the box to be defined in a GUI window, the position and size of the box can be visually defined and thus very convenient.
- Section 4.200.14.2 is added to the manual to illustrate how to use domain analysis module to visualize molecular cavity and calculate cavity volume.
- Section 4.19.2 is added to the manual to illustrate how to study variation of localized molecular orbitals (LMO) during chemical reaction. Section 4.19.3 is added to illustrate how to use LMO to analyze Re-Re quadruple bond in [Re2Cl8]2-.
- .molden file generated by ORCA with g angular moment basis functions now can be directly used as input file (without employing Molden2aim).
- "Set perspective" option is added to menu of all GUI windows for showing molecule, via this option one can exactly adjust viewpoint. In addition, in the GUI for showing relief map, text boxes are added to exactly control viewpoint.
- In Section 3.20.1 of Multiwfn manual, the way of plotting color-filled "RDG vs sign(lambda)rho" scatter map for studying weak interaction using NCI method is described.
- The functions 4,5,6 in hole-electron analysis module of Multiwfn is fully parallelized, the time cost is significantly lowered for large system.
- Orbital selection textbox is added to bottom-right corner of GUI of main function 0, so that orbital can be selected rapidly by simply inputting index. Beta orbitals can be selected by inputting negative index (e.g. inputting 7 and -9 means selecting the 7th alpha and the 9th beta orbitals, respectively).
- After booting up Multiwfn, if directly pressing ENTER button, a GUI window will be shown used to select input file.
- The built-in EDF library is updated (now it corresponds to molden2aim 4.1.4)
- Section 4.A.9 is added to manual. It describes how to calculate TrEsp (transition charge from electrostatic potential, see J. Phys. Chem. B, 110, 17268), and how to calculate excitonic coupling energy between two molecules based on TrEsp charges.
- When calculating ESP fitting charges (MK, CHELPG...), if radius of some elements are not predefined, now one can directly press ENTER button to use corresponding UFF radius multiplied by 1/1.2, this is often a reasonable choice.
- Speed of calculating transition dipole moment between excited state (subfunction 5 of main function 18) is greatly improved.

- For open-shell cases, the multi-center bond orders calculated based on NAO basis are not correct (prefactor is missing), this problem has been fixed.
- The sign of Mulliken transition charge outputted by hole-electron analysis module is not correct in the older versions, it should be multiplied by -1 to meet common convention. This problem has been fixed.

- The local total/dynamic/nondynamic electron correlation function proposed in J. Chem. Theory Comput., 13, 2705 (2017) now is supported as user-defined function 87,88,89, respectively. These functions are useful for vividly revealing electron correlation in various molecular regions. See corresponding entries in Section 2.7 for detail. Illustrative application is given in part 2 of Section 4.A.6.
- Spectrum of multiple systems now can be easily plotted together, see Section 4.11.6 for example.
- subfunction 2 of main function 100 now can yield basic input file for a batch of known quantum chemistry codes including Gaussian, GAMESS-US, ORCA, MOPAC, Dalton, MRCC, Molpro, NWChem, PSI, CFOUR and Molcas based on present geometry and charge/multiplicity.
- The CM5 charge proposed by Truhlar et al. in J. Chem. Theory Comput., 8, 527 (2012) has been supported as subfunction 16 of main function 7. See Section 3.9.14 of the manual for detail.
- The ghost-hunter index proposed by Adamo et al. in J. Comput. Chem., 38, 2151 (2017) is supported, it is automatically printed after hole-electron analysis is finished, see Section 3.21.7 of the manual for introduction. This index is useful to judge if an excited state calculated by TDDFT may be regarded as artificial ghost state.
- Gradient norm and Laplacian of electron density are added as user-defined function 79 and 80, respectively. The former is evaluated analytically, while the latter is evaluated semi-analytically.
- Electron delocalization range function EDR(r;d) and orbital overlap distance function D(r) are supported, the code is kindly contributed by Arshad Mehmood. Introduction is given as entry 20,21 of Section 2.6, illustrative examples can be found in Section 4.5.6, 4.5.7 and 4.12.8. Related references: J. Chem. Phys., 141, 144104 (2014); J. Chem. Theory Comput., 12, 3185 (2016); Angew. Chem. Int. Ed., 56, 6878 (2017).

- ORCA output file (CIS or TDA-DFT) has been formally supported for hole-electron analysis module, delta_r calculation module, NTO module and the module used to calculate transition dipole moment between excited states, see Section 3.21.1.2 for detail about the requirement on the input file. (TDDFT/TDHF output file may also be used, however, the result may be unreasonable when de-excitation is significant, see Section 3.21.1.2 for explanation)
- Output file of ORCA sTDA and sTD-DFT calculation now can be used as input file for plotting UV-Vis or ECD Spectrum via main function 11
- Better compatible with G16
- Anharmonic Raman and Anharmonic VCD spectra now can be plotted by main function 11 based on Gaussian output file of freq(raman,anharm) and freq(VCD,anharm) task, respectively (the latter is available only for G16)
- Main function -2 and -3 have been merged into main function 6 as subfunction -2 and -3.
- In subfunction 13 and 14 of main function 13, fragments can be directly defined by inputting atomic indices without preparing atomic list files. This change makes use of these functions more convenient.

- Hirshfeld-I (i.e. iterative Hirshfeld) is supported to calculate atomic charges, orbital composition and perform fuzzy space analysis. Please check Section 3.9.13 of the manual for introduction of its theory and implementation. Illustrative examples of using Hirshfeld-I to calculate atomic charges is given in Section 4.7.4
- Single exponential decay detector (SEDD) and Density overlap regions indicator (DORI) proposed in J. Chem. Theory Comput., 10, 3745 (2014) are supported as user-defined function 19 and 20, respectively. The advantage of DORI is that it can simultaneously reveal covalent and non-covalent interaction regions, and the pattern is similar to ELF+RDG. An example of using DORI is given at the end of Section 4.100.1.
- On-top pair density is supported as user-defined function 36.
- X, Y, Z component of Hamiltonian kinetic energy density have been added as 81, 82, 83th user-defined function, respectively. The counterpart of Lagrangian kinetic energy density have been supported as 84, 85, 86th user defined function, respectively.
- A new method to define plotting plane is added to main function 4 as mode 7. Via this mode one can directly define a plane parallel to a bond and meantime normal to a plane defined by three atoms. See Section 3.5.2 of the manual for detail.
- Pre-resonance Raman spectrum now can be plotted by option 2 of main function 11. Program will prompt the user to select the interested frequency of incident light.
- Subfunction 11 of main function 100 is greatly extended, now it can calculate both centroid distance and overlap between two orbitals. See Section 3.100.13 of the manual for details.
- By using option 4 and 8 of subfunction 2 of main function 100, .wfx file and NBO .47 file can be exported, respectively, the former is input file of GENNBO program.
- Pipek-Mezey orbital localization is supported as subfunction 13 of main function 200, please check Section 3.200.13 for detail and 4.200.13 for example.
- Energy of AdNDP orbitals now can be printed. Please check Section 3.17 for detail, the AdNDP examples in Section 4.14.1 and 4.14.3 have been correspondingly updated.
- Any real space function now can be integrated within isosurface of a given real space function by subfunction 14 of main function 200. Please check Section 3.200.14 of the manual for detail and Section 4.200.14 for example.
- A powerful EDF library provided by Wenli Zou is built-in. Now by default, if input file contains atoms using pseudopotential basis set, Multiwfn will automatically find proper EDF information for them to provide representation of inner-core density. See Appendix 4 of the manual for detail. (For .wfx file produced by Gaussian, by default Multiwfn still loads EDF field from this file rather than from the built-in EDF library).
- Natural transition orbital (NTO) analysis is supported as subfunction 6 of main function 18, please check Section 3.21.6 for detail and Section 4.18.4 for example.
- Coulomb attractive energy between hole and electron of an electronic excitation now can be calculated at post-process menu of subfunction 1 of main function 18, please check Section 3.21.1 for detail. The example in Section 4.18.1 is correspondingly updated.
- Conformational weighted spectrum and spectrum of multiple conformations now can be very conveniently plotted by main function 11. Please check Section 3.13.4 for detail and Section 4.11.4 for example. In addition, option 4 and 5 of spectrum plotting interface is improved, namely when changing setting of Y-axis at one side, you can choose to proportionally update range of Y-axis at another side so that their zero points are always in the same horizonal line.

- 32bit Windows version of Multiwfn will no longer be released. Since Multiwfn 3.4 only 64bit version will be released.
- The graphical effect of isosurface plotting has been improved, especially for transparent style
- When drawing isosurface with Linux and MacOS version, the requirement of the equal number of grids in X,Y,Z is removed.
- The style of atomic labels in plane map drawn by main function 4 now can be directly set by option 18 in post-process menu
- Two useful ways to check sanity of wavefunction are introduced as Appendix 4 of the manual
- The function of loading NBO plot file becomes more robust.
- .wfn file generated by Windows version of ORCA 4.0 is supported, and that generated by old version of ORCA is no longer supported
- GAMESS-US output file now can be used as input file (not comprehensively tested, currently only single point task at HF/DFT level is formally supported). The suffix of output file should be changed to .gms so that Multiwfn can properly recognize it
- Subfunction 7 of main function 6 now can output various kinds of integral matrix between basis functions, including overlap integrals, electric/magnetic dipole moment integrals, kinetic energy integrals and velocity integrals
- Density matrix in .fch will no longer be tentatively loaded since this version
- Atomic index in .molden file now is interpreted by Multiwfn as nuclear charge. Therefore, when pseudo-potential is used, you can manually change atomic index in the file so that Multiwfn can correctly recognize actual nuclear charge
- Loading speed of .fch and .molden file for large wavefunction is significantly improved

- Fixed a bug when loading NBO plot file with mixed spherical and cartesian shells.