Topology of molecular electron density and electrostatic potential with DAMQT

Abstract

A new version of the DAMQT package incorporating topological analysis of the molecular electron density and electrostatic potential is reported. Evaluation of electron density, electrostatic potential and their first and second derivatives within DAM partition–expansion is discussed, and the pertaining equations are reported. An efficient algorithm for the search of critical points, gradient paths, atomic basins and Hessian analysis is implemented using these equations. 3D viewer built in DAMQT incorporates new facilities for visualization of these properties, as well as for distance and angle measurements. Full control of projection mode is also added to the viewer in DAMQT. Some examples are provided showing the excellent performance for large molecular systems. Program summaryProgram Title: DAMQT_2.1Program Files doi: http://dx.doi.org/10.17632/2rxvgbsnhx.1Licensing provisions: GPLv3Programming language: Fortran90 and C++Supplementary material: Quick-start guide and User’s manual in PDF format included in the package. User’s manual is also accessible from the GUI.Nature of problem: Analysis and visualization of the molecular electron density, electrostatic potential, critical points, gradient paths, atomic basins, electric field and Hellmann–Feynman forces on nuclei.Solution method: The method of Deformed Atoms in Molecules, reported elsewhere[1], is used for partitioning the molecular electron density into atomic fragments, which are further expanded in spherical harmonics times radial factors. The partition is used for defining molecular density deformations and for the fast calculation of several properties associated with density, including topological analysis of electron density and electrostatic potential.Restrictions: Density must come from a LCAO calculation (any computational level) with spherical (not Cartesian) Slater or Gaussian functions.Unusual features: The program contains an OPEN statement to binary files (stream) in several files. This statement does not have a standard syntax in Fortran 90. Two possibilities are considered in conditional compilation: Intel’s ifort and Fortran2003 standard. This latter is applied to compilers other than ifort (gfortran uses this one, for instance).External routines/libraries: Qt (4.8 or higher), OpenGL (3.x or higher), freeGLUT 2.8.x