non-orthorhomic variable cell optimization

[monica]

Dear Rad,

I was running recently several triclinic cell optimization jobs
(although the angles are very close to 90), with variable hydrostatic
pressure (0-20 GPa), and it seemed to work: when comparing the volume
with similar orthorhombic cell, optimized manually (energy volume
curve). See output below for example. In my case, when the cell was
already close to the minimum, only minor changes occurred.

Monica


output for example
 CELL| Volume
[ANGSTROM**3]:                                            1798.737
 CELL| Vector a [ANGSTROM]:       9.814     0.000     0.000    |a|
=       9.814
 CELL| Vector b [ANGSTROM]:       0.424     9.038     0.000    |b|
=       9.048
 CELL| Vector c [ANGSTROM]:       1.575     0.001    20.279    |c|
=      20.340
 CELL| Angle (b,c)
[degree]:                                              89.790
 CELL| Angle (a,c)
[degree]:                                              85.559
 CELL| Angle (a,b)
[degree]:                                              87.314
 CELL| Grid size for subcell
generation                                    2.000
 CELL| Volume
[ANGSTROM**3]:                                            1795.645
 CELL| Vector a [ANGSTROM]:       9.807     0.000     0.000    |a|
=       9.807
 CELL| Vector b [ANGSTROM]:       0.424     9.031     0.000    |b|
=       9.041
 CELL| Vector c [ANGSTROM]:       1.575    -0.001    20.276    |c|
=      20.337
 CELL| Angle (b,c)
[degree]:                                              89.795
 CELL| Angle (a,c)
[degree]:                                              85.559
 CELL| Angle (a,b)
[degree]:                                              87.312
 CELL| Grid size for subcell
generation                                    2.000
 CELL| Volume
[ANGSTROM**3]:                                            1785.878
 CELL| Vector a [ANGSTROM]:       9.783     0.000     0.000    |a|
=       9.783
 CELL| Vector b [ANGSTROM]:       0.424     9.008     0.000    |b|
=       9.018
 CELL| Vector c [ANGSTROM]:       1.574    -0.006    20.266    |c|
=      20.327
 CELL| Angle (b,c)
[degree]:                                              89.810
 CELL| Angle (a,c)
[degree]:                                              85.560
 CELL| Angle (a,b)
[degree]:                                              87.307






On Feb 11, 10:47 pm, Rad <rad.... at arl.army.mil> wrote:
> Hello everybody,
>
> We seem to be having an issue with non-orthorhombic cell optimization
> when the lattice has all the three angles other than 90 degrees. Here
> is what appears to be happening: After the initial set up, the module
> Changes the lattice vectors by keeping the lengths the same but the
> angles are slightly different. This happens only when all the angles
> are not 90-degrees. The regtest for non-orthorhombic includes only one
> angle 120 and the rest are 90s. So the scenario I described might be
> missed out. This issue we have observed in several executables we have
> built over the last several months and on multiple architectures.
>
> ==================================================================================
> Here is the output just after the set up which is the same as the
> input:
> CELL| Volume
> [ANGSTROM**3]:                                             442.524
>  CELL| Vector a [ANGSTROM]:       9.010     0.000     0.000    |a|
> =       9.010
>  CELL| Vector b [ANGSTROM]:      -4.510     7.821     0.000    |b|
> =       9.028
>  CELL| Vector c [ANGSTROM]:      -0.216    -2.630     6.280    |c|
> =       6.812
>  CELL| Angle (b,c)
> [degree]:                                             108.580
>  CELL| Angle (a,c)
> [degree]:                                              91.820
>  CELL| Angle (a,b)
> [degree]:                                             119.970
>
> Here is when it got changed just before the first step of the
> optimization:
>
>  CELL| Volume
> [ANGSTROM**3]:                                             449.960
>  CELL| Vector a [ANGSTROM]:       9.010     0.000     0.000    |a|
> =       9.010
>  CELL| Vector b [ANGSTROM]:      -4.510     7.821     0.000    |b|
> =       9.028
>  CELL| Vector c [ANGSTROM]:      -0.216    -2.363     6.386    |c|
> =       6.812
>  CELL| Angle (b,c)
> [degree]:                                             106.534
>  CELL| Angle (a,c)
> [degree]:                                              91.820
>  CELL| Angle (a,b)
> [degree]:                                             119.970
>  CELL| Grid size for subcell
> generation                                    2.000
>
>  --------  Informations at step =     0 ------------
>   Optimization Method        =                   SD
>   Total Energy               =      -386.4717739715
>   Internal Pressure [bar]    =     18296.7247113471
>  ---------------------------------------------------
>
>  --------------------------
>  OPTIMIZATION STEP:      1
> =================================================================================
> Could someone please take a look at this issue and let me know what
> might be the issue.
>
> Thanks
> Rad