I am calculating elastic constant of Mg2Si (C11=126, C12=26, C44=48) experimental. Now using the formula by S. Q. Wang, H. Q. Ye, J. Phys. condense matter. using all the three equation, i am getting, 109, 25, 47 (C11, C12, C44) respectively.
But using only Eq. (6) and (7) only, I am getting 121, 20, 47 GPa, So can you please elaborate, whether, by using two equations, and by fitting the graphs, is it correct to find all the three elastic constants? Bipul Rakshit PhD in Physics Computational Research Lab. Barkatullah University, Bhopal 462 026, India Mob.: +919713445650 --- On Thu, 16/7/09, Sushil Auluck <saul...@iitk.ac.in> wrote: From: Sushil Auluck <saul...@iitk.ac.in> Subject: Re: [SIESTA-L] [*] Re: [SIESTA-L] [*] Re: [SIESTA-L] question about elastic constant To: SIESTA-L@listserv.uam.es Date: Thursday, 16 July, 2009, 7:04 PM bipul, you are absolutely right...to get 3 elastic constants you have to do 3 calculations for 3 different strains....as you have written. s.auluck > Respected Sir, > Sorry for so many queries. > > In the paper of S Q Wang et al. J Phys. Cond. Matter 15 (2003) 5307, > He uses three types of strains > > 1. Tri-axial shear strain to calculate C44 > 2. volume conservative orthorombic strain to calculate shear modulus C` > and > 3. Hydrostatic pressure to calculate Bulk modulus. > > In my calculations, on applying the 3rd strain, I am getting different > volumes (Volume non-conserve) and 1st & 2nd type volume remain conserve. > > > Because in order to calculate 3 elastic constants (C11, C12 and C44) we > require 3 equations, so do I have to use the above three equations, both > type (volume conservative and non-conservative) to calculate a single set > of elastic constants? > > > > > > Bipul Rakshit > > PhD in Physics > > Computational Research Lab. > > Barkatullah University, > > Bhopal 462 026, India > > Mob.: +919713445650 > > --- On Wed, 15/7/09, Sushil Auluck <saul...@iitk.ac.in> wrote: > > From: Sushil Auluck <saul...@iitk.ac.in> > Subject: Re: [*] Re: [SIESTA-L] question about elastic constant > To: "bipul rakshit" <bipu...@yahoo.co.in> > Date: Wednesday, 15 July, 2009, 8:56 PM > > bipul, > you can have 2 kinds of strains...volume conserving > and volume non conserving...each gives different > elastic constants..... > s.auluck > >> Dear Sir, >> I have one more doubt, that, if I calculate the set of lattice vector, >> applying the following strains >>   e = (δ, δ, (1 + δ)^ (−2) − 1, 0, 0, 0) >> >> as given in the paper attached with this mail, >> >> then the cell volume was not remain constant for all the lattice >> vectors. >> Means for different lattice vectors, the cell volume changes. >> >> But for other two set of strains >> e = (0, 0, 0, δ, δ, δ) >> and e =(δ, δ, δ, 0, 0, 0) >> the cell volume doesnt change for all the lattice vector. >> >> So is it the correct method I am applying? Or there should be no change >> of >> cell volume? >> >>  delta E/V = 6*C*δ^2 + O(δ^3 >> ).                        >> (7) >> V >> >> >> Bipul Rakshit >> >> PhD in Physics >> >> Computational Research Lab. >> >> Barkatullah University, >> >> Bhopal 462 026, India >> >> Mob.: +919713445650 >> >> --- On Wed, 15/7/09, Sushil Auluck <saul...@iitk.ac.in> wrote: >> >> From: Sushil Auluck <saul...@iitk.ac.in> >> Subject: Re: [*] Re: [SIESTA-L] question about elastic constant >> To: bipu...@yahoo.co.in >> Date: Wednesday, 15 July, 2009, 7:01 PM >> >> bipul, >> if you look at the derivation you will find terms like (1+d)**(1/2) >> or (1+d)**(1/3)....d is delta.....so when you expand using binomial >> theorem you will terms linear in d, quadratic in d, and cubic in d... >> in this context the series is terminated after the quadratic and so >> the remaining terms ( these are niglected) are order d**3..... >> s.auluck >> >>> Respected Sushil Auluck, >>> Thanks for your kind reply. As you said that the term means of order >>> delta >>> cube. >>> But I just want to know the equation of that term. Means how that order >>> delta cube, mathematically looks like. I asked this because, using that >>> equation, I have to find the elastic constants. >>> regards >>> >>> Bipul Rakshit >>> >>> PhD in Physics >>> >>> Computational Research Lab. >>> >>> Barkatullah University, >>> >>> Bhopal 462 026, India >>> >>> Mob.: +919713445650 >>> >>> --- On Mon, 13/7/09, Sushil Auluck <saul...@iitk.ac.in> wrote: >>> >>> From: Sushil Auluck <saul...@iitk.ac.in> >>> Subject: Re: [SIESTA-L] question about elastic constant >>> To: SIESTA-L@listserv.uam.es >>> Date: Monday, 13 July, 2009, 9:48 PM >>> >>> hi, >>> that means terms of order delta cubed (delta**3)...... >>> s.auluck >>> >>>> Dear Siesta Users, >>>> I have read the paper >>>> "S. Q. Wang, H. Q. Ye, J. Phys.: Condens. Matter 15 (2003) p. 5307." >>>>  >>>> Most of the thing is clear to me, except in Equation (7) what is >>>> "O(δ^3)" >>>> ? What does 'O' here. >>>> >>>> >>>> Please guide me for the same. >>>> >>>> >>>> Bipul Rakshit >>>> >>>> PhD in Physics >>>> >>>> Computational Research Lab. >>>> >>>> Barkatullah University, >>>> >>>> Bhopal 462 026, India >>>> >>>> Mob.: +919713445650 >>>> >>>> >>>>     See the Web's breaking stories, chosen by people >>>> like you.. >>>> Check >>>> out Yahoo! Buzz. http://in.buzz.yahoo.com/ >>> >>> >>> ......................................................................... >>> Prof. Sushil Auluck          >>>  >>> Phone:+91-512-6797092/6148 >>> Department of Physics          >>>    >>> +91-512-6798177(Home) >>> Indian Institute of Technology       Cell >>> :+91-9305548667 >>> Kanpur 208016 (UP)          >>>    Fax >>> :+91-512-6790914 >>> India             >>>      >>> E-mail:saul...@iitk.ac.in    >>>  >>>    ................................................:saul...@gmail.com >>> http://www.iitk.ac.in/phy/People/phy_facvis.html >>> http://www.iitk.ac.in/phy/New01/profile_SA.html >>> ......................................................................... >>> ~ >>> >>> >>> >>>     See the Web's breaking stories, chosen by people >>> like you. >>> Check >>> out Yahoo! Buzz. http://in.buzz.yahoo.com/ >> >> >> ........................................................................ >> Prof. Sushil Auluck          >>  >> Phone:+91-512-6797092/6148 >> Department of Physics          >>    >> +91-512-6798177(Home) >> Indian Institute of Technology       Cell >> :+91-9305548667 >> Kanpur 208016 (UP)          >>    Fax >> :+91-512-6790914 >> India             >>      >> E-mail:saul...@iitk..ac.in    >>  >>    ................................................:saul...@gmail.com >> http://www.iitk.ac.in/phy/People/phy_facvis.html >> http://www.iitk.ac.in/phy/New01/profile_SA.html >> ........................................................................ >> ~ >> >> >> >>     See the Web's breaking stories, chosen by people like you. >> Check >> out Yahoo! Buzz. http://in.buzz.yahoo.com/ > > > ........................................................................ > Prof. Sushil Auluck           > Phone:+91-512-6797092/6148 > Department of Physics             > +91-512-6798177(Home) > Indian Institute of Technology       Cell :+91-9305548667 > Kanpur 208016 (UP)             Fax > :+91-512-6790914 > India                  > E-mail:saul...@iitk..ac.in    >     ................................................:saul...@gmail.com > http://www.iitk.ac.in/phy/People/phy_facvis.html > http://www.iitk.ac.in/phy/New01/profile_SA.html > ........................................................................ > ~ > > > > Love Cricket? Check out live scores, photos, video highlights and > more. Click here http://cricket.yahoo.com ........................................................................ Prof. Sushil Auluck Phone:+91-512-6797092/6148 Department of Physics +91-512-6798177(Home) Indian Institute of Technology Cell :+91-9305548667 Kanpur 208016 (UP) Fax :+91-512-6790914 India E-mail:saul...@iitk..ac.in ...............................................:saul...@gmail.com http://www.iitk.ac.in/phy/People/phy_facvis.html http://www.iitk.ac.in/phy/New01/profile_SA.html ........................................................................ ~ Looking for local information? Find it on Yahoo! Local http://in.local.yahoo.com/
