# [Pw_forum] program modification of virtual.f90 2 (different riiner)

yukihiro_okuno at fujifilm.co.jp yukihiro_okuno at fujifilm.co.jp
Fri Mar 21 14:38:48 CET 2008

```Dear PW users and developer.

This is self responce.

I wrote  mistake in former e-mail

>The modification of virtual.f90  when A atom and B atom is mixed by the
ratio  A:B= x:1-x ,  I planed  the modification like ,

>1)    We set new riiner = min(r_{A}.r_{B})    for each angular momentum L
for the virtual atom.

>2)   then  we make virtual potential like

>    r < min(r_{A}. r_{B}) = r_{A}  = r_inner     ( we set r_{A} < r_{B} )

>    upf_qfcoef(n,m) = x * qfcoef_{A}      (where  n, m is for A atom index
and qfcoef is A atom pseudized polynomial  coefficient C1,C2....)

>   upf_qfcoef(n,m)  = (1-x) * qfcoef_{B} (where  n,m is for B atom index
and qfcoef is B atom pseudized  polynomial coefficient )

>    r_{A} < r < r_{B}

>   qfun(n,m)[r}  = x * r^{L} * (C1_{A} + C2_{A} * r^{2} + C3_{A} * r^{4} +
...)

>   qfun(n,m)[r] = (1-x) * qfun_{B}    ( where qfun is the argumentation
function for r > riiner which are specified in UPF file ).

>    r_{B} < r

>    qfun(n,m)[r}  = x * qfun_{A}

>   qfun(n,m)[r] = (1-x) * qfun_{B}

In the range r_{A} < r < r_{B}  , where r_{A} and r_{B} is A and B atom's
rinner,

I was going to write like

qfun(n,m)[r}  = x * qfun_{B}(r)  ( where qfun is the argumentation
function for r > riiner which are specified in UPF file ).

qfun(n,m)[r] = (1-x) * r^{L} * (C1_{B} + C2_{B} * r^{2} + C3_{B} * r^{4}
+ ...)

But qfun(n,m) should be L independent,  so  it cannot apply UPF format.

So if we apply the VCA approximation for different riiner,  it should be
r_{VCA} = r_{B}  ( where r_{VCA} is virtual atom's riiner)

and give new polynomial coefficient C_{A}  which fit the new function
below,

Q^{L}(r)  =    r^{L} * (C1_{A} + C2_{A} * r^{2} + C3_{A} * r^{A} + ...)   (
r < r_{A} )

=    qfun_{A} (r)       ( r_{A} <  r < r_{B} ) .

Or is it easy to make pseudo potential with same riiner insted of
modifying virtual.f90 or other source codes ?

Yukihiro Okuno

```

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