I'm afraid the formula for calculating cosA should be cosA = b (*) c / (|b| | c|)
dr. zhou huiqun @earth sciences, nanjing university, china ----- Original Message ----- From: GAO Zhe To: PWSCF Forum Sent: Wednesday, November 16, 2011 8:53 PM Subject: Re: [Pw_forum] calculation of lattice parameter and angle of rhombohedral structure the three basis vectors of rhombohedral are (after relaxation) : a = ( 0.636439417 -0.367448469 0.640642896 ) b = ( 0.000000000 0.734896938 0.640642896 ) c = ( -0.636439417 -0.367448469 0.640642896 ) then the lattice paremeter should be: A = sqrt (a1^2+a2^2+a3^2) * alat = 8.05092296 a.u. . The angle between two vectors can be calculated by: cosA = a (*) b / |a (*) b|, where a and b are basis vectors, (*) represents the dot product. -- GAO Zhe CMC Lab, MSE, SNU, Seoul, S.Korea At 2011-11-16 20:14:38,"yedu kondalu" <nykondalu at gmail.com> wrote: Dear users, I did the optimization for a compound using variable cell approximation using PWSCF, which belongs to the space group R3m(160) Rhombohedral representation. The primitive vectors in terms of lattice parameter a = 8.25791360 a.u. a(1) = ( 0.619505 -0.357671 0.698774 ) a(2) = ( 0.000000 0.715343 0.698774 ) a(3) = ( -0.619505 -0.357671 0.698774 ) after completion of optimization step, the primitive vectors CELL_PARAMETERS (alat= 8.25791360) 0.636439417 -0.367448469 0.640642896 0.000000000 0.734896938 0.640642896 -0.636439417 -0.367448469 0.640642896 can u please explain me how can I calculate the lattice parameter a and the angle (alpha) ??? Thanks in advance Regards Yedukondalu ------------------------------------------------------------------------------ _______________________________________________ Pw_forum mailing list Pw_forum at pwscf.org http://www.democritos.it/mailman/listinfo/pw_forum -------------- next part -------------- An HTML attachment was scrubbed... URL: http://www.democritos.it/pipermail/pw_forum/attachments/20111117/7d69cfca/attachment-0001.htm