Multiwfn forum

Alexey

Member

Registered: 2024-06-28

Posts: 15

modify function

i need to modify this part of 'calchessmat_prodens' subroutine to get good promolecular density and calculate its derivatives for all elements. the following part of code doesnt calculate derivatives in the nuclear positions (but value of promolecular density is good calculated), however, in non-nuclear positions the derivative is calculated normally, what should I write in the following code to get derivatives in nuclear positionsn? (i ask this because if i use "output prop in point" for the iuserfunc==-2 function then i get derivatives at nuclear positions, but in the case below (elerho from my new calchessmat_prodens) i don't get derivatives of elerho in nuclear positions, only value)

if (iele>=1) then if (r>atmrhocut(iele)) cycle call genatmraddens(iele,rhoarr,npt) !Extract spherically averaged radial density of corresponding element at specific grids if (idohess==0) then call lagintpol(atmradpos(1:npt),rhoarr(1:npt),npt,r,term,der1r,der2r,2) else if (idohess==1) then call lagintpol(atmradpos(1:npt),rhoarr(1:npt),npt,r,term,der1r,der2r,3) end if elerho=elerho+term der1rdr=der1r/r derx=derx+der1rdr*rx dery=dery+der1rdr*ry derz=derz+der1rdr*rz if (idohess==1) then tmpval=(der2r-der1rdr)/r2 dxx=dxx+der1rdr+tmpval*rx2 dyy=dyy+der1rdr+tmpval*ry2 dzz=dzz+der1rdr+tmpval*rz2 dxy=dxy+tmpval*rx*ry dyz=dyz+tmpval*ry*rz dxz=dxz+tmpval*rx*rz end if end if

Last edited by Alexey (2024-07-08 23:46:41)

sobereva

Tian Lu (Multiwfn developer)

From: Beijing

Registered: 2017-09-11

Posts: 1,762

Website

Re: modify function

Derivative at nuclear position cannot be obtained. In the case of good promolecular density, for each element, Multiwfn has an array recording radial density of its isolated state, and Lagrangian interpolation is used to obtain the value and derivatives at any radial distance. At nuclear position, the interpolation is not feasible, because it is the starting position of radial density.

In fact, it is well-known that electron density at nuclear position is ill-defined, because there is a cusp of electron density at this point (seehttps://en.wikipedia.org/wiki/Kato_theorem).