[CPMD-list] Problems optimizing monoclinic unit cell

[Axel Kohlmeyer]

On Mon, 6 Dec 2004, Ewald Pauwels wrote:

dear ewald,

[...]

EW> This calculation was succesfull, but now in the output it appears that 
EW> my molecular symmetry is TRICLINIC!!

this is to be expected. if you use CELL VECTORS, cpmd does not even 
try to detect cell symmetry and thus assumes a triclinic cell (and
cannot take advantage of the symmetry).

EW>       ************************** SUPERCELL ***************************
EW>       SYMMETRY:                                              TRICLINIC
EW>       LATTICE CONSTANT(a.u.):                                  9.61304
EW>       CELL DIMENSION:   9.6130  2.3143  1.0733  0.0000 -0.3744  0.0000
EW>       VOLUME(OMEGA IN BOHR^3):                              2046.13616
EW>       LATTICE VECTOR A1(BOHR):            9.6130     0.0000     0.0000
EW>       LATTICE VECTOR A2(BOHR):            0.0000    22.2477     0.0000
EW>       LATTICE VECTOR A3(BOHR):           -3.8635     0.0000     9.5673
EW> 
EW> Eventually, my calculations succeeded but I hope you agree that there 
EW> are certain issues with regard to the SYMMETRY and CELL keywords that 
EW> need to be looked at.

as far as i understand it - please correct me anybody, if i am mistaken,
i'd really like to be certain about this - you have give the cell dimensions 
for the _conventional_ cell (but only the atom positions for the primitive cell). 
i know at least one more code, that uses the exact same conventions, so 
i am pretty sure, that this is intentionally so.

best regards,
	axel.


EW> 
EW> 
EW> Sincerely,
EW> Ewald Pauwels.
EW> 
EW> 
EW> 
EW> 
EW> Ewald Pauwels wrote:
EW> 
EW> > Dear all,
EW> >
EW> > Does anybody have any experience with applying CPMD on monoclinic 
EW> > crystals?
EW> > The system I am studying contains four (organic) molecules in the unit 
EW> > cell. When I optimize these molecules (only the atomic coordinates - 
EW> > not the cell constants), I find that the unit cell no longer satisfies 
EW> > the original symmetry. I.e. all four molecules have a substantially 
EW> > different conformation!
EW> >
EW> > I suspect that I must be doing something wrong here. Below is my 
EW> > inputfile.
EW> >
EW> >
EW> > Thanks in advance,
EW> > Ewald.
EW> >
EW> >
EW> >
EW> > -------------------------------------------------------
EW> > inputfile
EW> > -------------------------------------------------------
EW> > &CPMD
EW> > RESTART LATEST GEOFILE WAVEFUNCTION
EW> > OPTIMIZE GEOMETRY
EW> > LSD
EW> > ODIIS NO_RESET=50
EW> >  10
EW> > TIMESTEP
EW> >  20
EW> > PRINT
EW> >  10
EW> > STRUCTURE BONDS ANGLES
EW> > &END
EW> >
EW> > &SYSTEM
EW> > ANGSTROM
EW> > SYMMETRY
EW> > 12
EW> > CELL
EW> > 5.0872  2.314338  1.073321  0.0  -0.374493314  0.0
EW> > CUTOFF
EW> > 25.
EW> > MULTIPLICITY
EW> > 1
EW> > &END
EW> >
EW> > &ATOMS
EW> > *C_VDB_U BINARY NEWF
EW> > LMAX=P
EW> > 8
EW> >  0.218182218417937  1.473520453  0.333090471110274
EW> >  0.732546560623109  1.717103823  -1.08374897292691
EW> >  1.30308357695184  7.360020453  2.1982999039374
EW> >  0.788719234746671  7.603603823  3.61513934797459
EW> >  -0.218182218417937  -1.473520453  -0.333090471110274
EW> >  -0.732546560623109  -1.717103823  1.08374897292691
EW> >  1.73944801378772  4.412979547  2.86448084615795
EW> >  2.25381235599289  4.169396177  1.44764140212077
EW> > *N_VDB_U BINARY NEWF
EW> > LMAX=P
EW> > 4
EW> >  2.03113800324446  1.040509513  -1.31410549705625
EW> >  -0.509872207874679  6.927009513  3.84549587210393
EW> >  -2.03113800324446  -1.040509513  1.31410549705625
EW> >  3.55240379861424  4.845990487  1.21728487799143
EW> > *O_VDB_U BINARY NEWF
EW> > LMAX=P
EW> > 8
EW> >  1.05333382374583  1.104201443  1.19695275049904
EW> >  -1.00750738194352  1.676251513  0.53944941448416
EW> >  0.467931971623952  6.990701443  1.33443762454863
EW> >  2.5287731773133  7.562751513  1.99194096056352
EW> >  -1.05333382374583  -1.104201443  -1.19695275049904
EW> >  1.00750738194352  -1.676251513  -0.53944941448416
EW> >  2.57459961911561  4.782298557  3.72834312554672
EW> >  0.513758413426261  4.210248487  3.07083978953184
EW> > *H_VDB_U BINARY NEWF
EW> > LMAX=S
EW> > 20
EW> >  2.33817143317496  1.18130282  -2.29299415508719
EW> >  2.75812420631155  1.37791192  -0.67745575495101
EW> >  1.93653355901116  0.03473035  -1.14763114043162
EW> >  0.875530385150063  2.77889892  -1.22357285168305
EW> >  0.0131007466085907  1.35318862  -1.81758891709173
EW> >  -0.816905637805185  7.06780282  4.82438453013487
EW> >  -1.23685841094177  7.26441192  3.20884612999869
EW> >  -0.415267763641377  5.92123035  3.67902151547929
EW> >  0.645735410219716  8.66539892  3.75496322673072
EW> >  1.50816504876119  7.23968862  4.34897929213941
EW> >  -2.33817143317496  -1.18130282  2.29299415508719
EW> >  -2.75812420631155  -1.37791192  0.67745575495101
EW> >  -1.93653355901116  -0.03473035  1.14763114043162
EW> >  -0.875530385150063  -2.77889892  1.22357285168305
EW> >  -0.0131007466085907  -1.35318862  1.81758891709173
EW> >  3.85943722854474  4.70519718  0.23839621996049
EW> >  4.27939000168133  4.50858808  1.85393462009667
EW> >  3.45779935438094  5.85176965  1.38375923461606
EW> >  2.39679618051984  3.10760108  1.30781752336463
EW> >  1.53436654197837  4.53331138  0.713801457955944
EW> > &END
EW> >
EW> > &DFT
EW> > LDA CORRELATION PZ
EW> > FUNCTIONAL BP
EW> > GC-CUTOFF
EW> > 5.D-5
EW> > &END
EW> > ------------------------------------------------------------------
EW> >
EW> >
EW> >
EW> >
EW> >
EW> >
EW> 
EW> 
EW> 

-- 

=======================================================================
Dr. Axel Kohlmeyer   e-mail: axel.kohlmeyer at theochem.ruhr-uni-bochum.de
Lehrstuhl fuer Theoretische Chemie          Phone: ++49 (0)234/32-26673
Ruhr-Universitaet Bochum - NC 03/53         Fax:   ++49 (0)234/32-14045
D-44780 Bochum  http://www.theochem.ruhr-uni-bochum.de/~axel.kohlmeyer/
=======================================================================
If you make something idiot-proof, the universe creates a better idiot.