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["Allan, Douglas C Dr" <AllanDC@corning.com>]

Adam,

 

The word “columnwise” in this context means that the first 3 numbers you enter will fill out the first column and so forth.  You never enter numbers columnwise when you are reading files line by line, you just enter numbers.  It is not a misprint or typo.

 

Also do not overlook the role of the length scale, which is defined independently of rprim.  Rprim gets normalized after input so it represents directions that are of unit length.

 

Cheers,

Doug

 

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From: Adam Sorini [mailto:asorini@gmail.com]
Sent: Monday, October 20, 2008 6:28 PM
To: forum@abinit.org
Subject: Re: [abinit-forum] Definition of rprim

 

It's my understanding that

rprim a b c
        d e f
        g h i

mean that the primative vectors are R1 = (a,b,c), R2 = (d,e,f), R3 = (g,h,i) and the matrix rprim(i,j) is
rprim(i,j) = Rj(i)

So, I think that's what they mean by "columnwise". Just that the first index of array rprim(i,j) gives the components of the primative lattice vector. The use of the word "columnwise" in the first sentence of the description of the basic input variable rprim then appears to be a mistake since we don't write the vectors in the input file "columnwise". Cheers,

Adam

On Mon, Oct 20, 2008 at 2:17 PM, Anindya Roy <royanin@gmail.com> wrote:

Hi all,

I'm having a little trouble to interpret the basic definition of
'rprim' as stated in documentation of version 5.5.4 (and similar
ones): rprim is defined to be  "...in columnwise entry, the three
dimensionless primitive translations in real space."

Later the example given for hexagonal lattice:

"rprim  0.86602540378  0.5  0.0
     -0.86602540378  0.5  0.0
      0.0            0.0  1.0

that can be avoided thanks to angdeg:

angdeg 90 90 120
"

It looks to me that new basis vectors are in row wise entry, rather
than column wise.

So if we assume that the new vector R_1 is [rprim(11)\hat{x} +
rprim(12) \hat{y} + rprim(13) \hat{z}] , then it's internally
consistent how xred and xcart are converted among themselves. Am I
missing something obvious? Your thought will be greatly appreciated.

Thanks,
Anindya Roy
Graduate student
Rutgers University, USA