[Pw_forum] possible bug in scatter_forw.f90

[Manoj Srivastava]

Dear All, 
 Is any body familiar with the scatter_forw.f90 subroutine of PWCOND? I
think there is a bug in this subroutine at the place where you calculate
intw2, which is z integration of nonlocal wavefunction with beta function.
I have looked up the necessary formulae in the Choi & Ihm's paper (PRB 59,
2267, Jan 1999). In the paper, nonlocal wavefunction has 3 terms, one of
which contains beta function, say W. The other two parts dont have any W
in them, rather they are just plane wave solution. (Please have a look at
equation 24 and 26 of the paper ). So, when we are doing z integration of
nonlocal wavefunction with beta function W, we should have three terms,
one of which should contain two W, but rest should just have one W. On the
other hand in the code all three terms contain two beta functions!!
(please have a look at line 228 of scatter_forw.f90). I am wondering if my
understanding is right? 
I have one more question in the later part of the same subroutine. What
does the lapack subroutine 
ZGESV(2*n2d,2*n2d+norb*npol,amat,2*n2d,ipiv,xmat,2*n2d,info)
do? 
I tried to look it up and i got the idea that it is trying to solve 
amat*x=xmat, with amat and xmat known and x unknown, and at the end of
calculation it stores x in xmat. 
so, basically it does--  x=[(amat)^(-1)]*xmat. Am i right? So, it changes
the structure of xmat from what is defined in 'constructs matrices'
part. Is it correct? 
Also, afterwards in this code where  it 'rotates integrals' is not very
clear to me. 
Could somebody please tell me in little detail, what is going on
here? Also, is this subroutine written just on the basis of Choi and Ihm
paper, or are there more reference to it? If yes, would someone mind
mentioning them? 

Regards, 
Manoj Srivastava 
Physics Graduate Student 
University of Florida, 
Gainesville,FL, USA