Thank you very much sir, now I have gotten a cl ear picture of how to calculate celldm(4)-celldm(6) Now my question is that in the case where celldm(4)=0.00 for monoclinic structure can we say the crystal structure is similar or same as that of orthorhombic sinc On Mon, Feb 22, 2016 at 9:54, Giovanni Cantele<[email protected]> wrote: > On 20 Feb 2016, at 20:34, Ridwan Agbaoye <[email protected]> wrote: > > Please I need clarification on how to compute celldm(4), celldm(5) and > celldm(6) for ibrav 12, 13 and 14 > > I have conflicting opinion on how it should be calculated though it is stated > as for ibrav =12 and 13 celldm(4)=cos(ab),for ibrav 14 celldm(4)=cos(bc), > celldm(5)=cos(ac)and celldm(6)=(ab). Although cos(ab) is the cosine of angle > between lattice parameters a and b as stated in INPUT_PW.HTML of quantum > espresso > > Please I need clarifications > > Agbaoye Ridwan Olamide > Federal University of Agriculture, Abeokuta > M.Sc. (in view) > _______________________________________________ > Pw_forum mailing list > [email protected] > http://pwscf.org/mailman/listinfo/pw_forum
Example for ibrav=12 cosAB = cosine of the angle between axis a and b (gamma) So if you know the lattice vector coordinates, that is, a=(ax,ay,az) and b=(bx,by,bz), just calculate cosAB = a . b / ( |a| |b| ) where a . b = dot product of a and b = ax bx + ay by + az bz |a| = length of vector a = sqrt( ax^2 + ay^2 + az^2 ) and same for |b|. Instead, if you know, directly gamma, just compute cos( gamma ). Similar consideration apply to cos(bc) and cos(ac) for the other lattices. Giovanni -- Giovanni Cantele, PhD CNR-SPIN c/o Dipartimento di Fisica Universita' di Napoli "Federico II" Complesso Universitario M. S. Angelo - Ed. 6 Via Cintia, I-80126, Napoli, Italy e-mail: [email protected] Phone: +39 081 676910 Skype contact: giocan74 ResearcherID: http://www.researcherid.com/rid/A-1951-2009 Web page: http://people.na.infn.it/~cantele _______________________________________________ Pw_forum mailing list [email protected] http://pwscf.org/mailman/listinfo/pw_forum
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