CASINO manual - Theory of Condensed Matter

More documents

Recommendations

Info

--parallel e.g. linuxpc-ifort-parallel - Clusters with queueing systems: ---parallel e.g.linuxpc-ifort-pbs-parallel • ‘Extended’ CASINO ARCHs are intended to represent specific systems, and are usually modifications to existing generic CASINO ARCHs. Their name is of the form: . e.g. linuxpc-ifort.berts-weird-computer The corresponding .arch file is typically intended to ‘include’ its generic counterpart, if it exists, but again this is just a guideline. See the files in the CASINO/arch/data directory for the range of both generic and extended CASINO ARCH names. If you end up generating your own unique .arch file then you may send it to Mike Towler (mdt26 at cam.ac.uk) who can incorporate it permanently into the distribution. Very large machines in national computer facilities often have specialized setups and requires Extended CASINO ARCHs. Some examples of current top-of-the-range hardware: . • Titan (Oak Ridge, USA): linuxpc--pbs-parallel.titan where compiler is pgf, cray, ifort or gcc. • Hector (UK national facility): linuxpc-〈compiler〉-pbs-parallel.hector3 where 〈compiler〉 is pgf, path, cray or gcc. • Darwin (Cambridge HPCF facility, UK): linuxpc-ifort-pbs-parallel.darwin2 (Westmere partition) or linuxpc-ifort-pbs-parallel.darwin3 (Sandy Bridge partition) • Intrepid (IBM Blue Gene/P, Argonne, USA): bluegene-xlf-cobalt-parallel.intrepid. • Blue Joule (IBM Blue Gene/Q, Hartree Centre, U.K.) bluegene-xlf-ll-parallel.bluejoule The full syntax of .arch files is explained in the file CASINO/arch/README. This information is duplicated in Appendix 5 of this manual. 5.3 Further installation notes • The [r] option of the install script will restore the casino distribution directory to its original state for compilation purposes. This involves removing all binary executables, links to scripts, and compiler object files, which is achieved practically by removing the following directories: bin qmc, lib/zlib, src/zlib and utils/zlib. • If you use the vim, emacs, or gedit text editors then it is possible to configure them to highlight the syntax of casino’s arch files and the various input files. See the README file in CASINO/data/syntax or just select the [y] option of the install script to automatically do the configuration. • For versions of casino prior to 2.10, a different setup system was used, involving environment variables QMC ARCH and QMC ID (the latter for customization on specialized machines). These may be retained if you wish to continue to use older versions of the code, but the setup will need to be redone for version 2.10 and later. 5.4 Discussion forum An online discussion forum http://www.vallico.net/casino-forum exists, where users may discuss issues relating to quantum Monte Carlo and the casino code. Expert users of the code are known to haunt the forum, and thus it may be useful for soliciting advice if problems are encountered in installing or using casino. 10
6 Introductory user’s guide: how to use CASINO 6.1 Getting started This section gives basic practical details for running QMC calculations with casino, and is intended for new users. It assumes you already know something about the theory of VMC, DMC and wavefunction optimization. If you don’t then please see the standard references for general details about the methods (e.g., Refs. [10], [11], [12], [13], and the Theoretical Background section at the end of this manual). Following the instructions in this section will not necessarily lead to publication-quality results, but should at least allow you to play with the code and get some feel for how it works. 6.1.1 Trial wave functions Unless you’re interested in electron or electron–hole phases in the absence of an external potential, in which case you can start straight away, the first hurdle to doing research with casino is to generate a trial wave function using, for example, a DFT or HF calculation. Multideterminant quantum chemistry methods can also be used. This has to be done using an external program, which must either support casino directly, in that it is capable of writing out the wave function in a format that casino understands, or it must be supported indirectly by casino, in which case a conversion utility should be found under ~/CASINO/utils/wfn converters/ which can convert the information in its standard to output to casino format. Note that ‘writing out the wave function’ basically means writing out the geometry, the basis set and the coefficients that define the orbitals. The information defining the trial wave function generated by the external program lives in files whose name depends on the basis set in which the orbitals in the determinantal part of the wave function are expanded. These files are called gwfn.data (Gaussians), pwfn.data (plane waves), bwfn.data (blip functions), awfn.data (atomic orbitals given explicitly on a radial grid), dwfn.data (molecular orbitals for dimers given explicitly on a radial grid), or stowfn.data (Slater-type orbitals). These files will often be referred to generically with the name xwfn.data. For the case of blip orbitals, where the wave function file can get very large, you will often see the bwfn.data in its unformatted binary form bwfn.data.bin which takes up much less disk space (an older binary format bwfn.data.b1 is also supported). The choice of basis set has been found to depend largely on personal prejudice, though some consideration should be given to issues of computational efficiency. Gaussian, Slater-type, plane-wave and numerical atomic wave functions are taken directly from the generating code. The plane-wave DFT code pwscf/quantum espresso knows about blips, and is capable of internally transforming its plane-wave orbitals and writing out blip wave functions directly (in either binary or formatted forms). With other plane-wave DFT codes, the blip wave function files are generated by post-processing a plane-wave pwfn.data file using a casino utility called blip. It is desirable to carry out this transformation because plane waves are the worst possible basis set you could choose for QMC, since every basis function contributes at every point in space. Moreover, blips can be used to make the computer time for a casino calculation scale independently of system size (for energy-per-atom properties) or quadratically with system size (for total-energy properties). To achieve this, the delocalized orbitals generated by most DFT/HF programs need to undergo a linear transformation to a localized form, using the localizer utility before re-expanding in blips using the blip utility, though in practice this facility is rarely used. Generating trial wave functions currently requires you to have access to one of the codes listed in Sec. 8. If you don’t have access to any of these codes and have a specific system in mind, then Mike Towler is known for being able to generate trial wave functions in record time on payment of a suitable fee (just to get you started he likes, in no particular order: bright shiny things, books about romance, yummy things to eat, poems, authorship on papers for which he hasn’t really done any work, cute cuddly toys, especially bears, and money). If you are using pseudopotentials you must be able to use the same ones in the orbital-generating code and in casino: see the note in the next section for details. 6.1.2 Pseudopotentials casino is capable of running all-electron calculations, where core and valence electrons are explicitly included in the simulation, or pseudopotential calculations, where the core electrons are replaced by an effective potential. The latter approach is normally advantageous since the computer time required 11
Page 1 and 2: CASINO User’s Guide Version 2.13
Page 3 and 4: 8.6 GAUSSIAN94/98/03/09 . . . . . .
Page 5 and 6: 29.2 Fourier transformation of CASI
Page 7 and 8: 1 Introduction casino is a computer
Page 9 and 10: 3.2 Legal stuff casino is given awa
Page 11 and 12: - Grossman-Mitas DMC-DFT molecular
Page 13 and 14: Your defined setup can then be perm
Page 15: - : perform compilation (default).
Page 19 and 20: ATOM BASIS TYPE The basis used to r
Page 21 and 22: ENVMC v0.60: Script to extract VMC
Page 23 and 24: Std. err. in the mean DMC energy (a
Page 25 and 26: Jastrow factor from each cycle of t
Page 27 and 28: V(x) Ψ init (x) τ{ t Ψ 0 (x) x T
Page 29 and 30: the energy becomes roughly constant
Page 31 and 32: many cores, time limits etc, which
Page 33 and 34: Set the verbosity level of the mach
Page 35 and 36: 6.7 How to run coupled DFT-DMC mole
Page 37 and 38: unqmcmd --startqmc=M Start the chai
Page 39 and 40: config.out This is the name under w
Page 41 and 42: ‘slater-type’: use Slater-type
Page 43 and 44: CUSTOM SPAIR DEP (Block) This input
Page 45 and 46: initial configurations come from DM
Page 47 and 48: DTDMC (Real) Time step for DMC run
Page 49 and 50: FORCES INFO (Integer) Controls the
Page 51 and 52: nucleus is assumed to lie at the or
Page 53 and 54: MOVIECELLS (Logical) If F then casi
Page 55 and 56: OPT MAXITER (Integer) Largest permi
Page 57 and 58: of G vectors and discards all those
Page 59 and 60: half a million cores, it may be des
Page 61 and 62: VM REWEIGHT (Logical) If vm reweigh
Page 63 and 64: default this is 0 hartree. It shoul
Page 65 and 66: A very detailed specification of th
Page 67 and 68:
-1 0 0 1 1 1 1 1 1 1 0 2 1 0 1 2 Pa
Page 69 and 70:
cusp conditions; otherwise, only th
Page 71 and 72:
Detailed information about each of
Page 73 and 74:
|k| (outermost). Hence one can spec
Page 75 and 76:
large and the wave function is near
Page 77 and 78:
R(i) in atomic units 0.000000000000
Page 79 and 80:
2. The charge-density Fourier coeff
Page 81 and 82:
c_767: [ 996 ] ... Compressed expan
Page 83 and 84:
valence charges for each atom %%%%%
Page 85 and 86:
1988). This can be found online. An
Page 87 and 88:
1.3813695578425E+00 1.3957621401173
Page 89 and 90:
PWSCF Method: DFT DFT Functional: u
Page 91 and 92:
0.125203784849961E-01 0.13042462855
Page 93 and 94:
3.3000000000000E+00 2.0000000000000
Page 95 and 96:
Potential Number of grid points 200
Page 97 and 98:
9. Clearly, the total number of pos
Page 99 and 100:
EBEST (DMC only) Best estimate of t
Page 101 and 102:
Use G-vector set 1 Number of sets 2
Page 103 and 104:
1000.0 rho_a(G)*rho_b(-G) 16.0 4.12
Page 105 and 106:
total weight must always be include
Page 107 and 108:
The exporter does not currently wor
Page 109 and 110:
8.4.2 Generating gwfn.data files wi
Page 111 and 112:
After successfully running properti
Page 113 and 114:
% mv Test.FChk dna.Fchk run gaussia
Page 115 and 116:
• By default, gaussian uses spin
Page 117 and 118:
Routine Purpose qmc write Writes th
Page 119 and 120:
not the case the defaults can be ch
Page 121 and 122:
8.10 TURBOMOLE Website: www.turbomo
Page 123 and 124:
• crysgen06/09, crystaltoqmc: The
Page 125 and 126:
• quickblock: Simple reblocking u
Page 127 and 128:
• In Movie Settings choose Trajec
Page 129 and 130:
the move rejection probability is h
Page 131 and 132:
This leads to the single-electron d
Page 133 and 134:
In the UNR [19] scheme the modified
Page 135 and 136:
13.7 Evaluating expectation values
Page 137 and 138:
Population-control catastrophes sho
Page 139 and 140:
where u k has the periodicity of th
Page 141 and 142:
Although the constraint equations a
Page 143 and 144:
18 Wave-function updating Consider
Page 145 and 146:
19.2 Evaluating the nonlocal pseudo
Page 147 and 148:
of a unit point charge at r j in ev
Page 149 and 150:
19.4.3 1D Coulomb interaction Coulo
Page 151 and 152:
To investigate whether the extrapol
Page 153 and 154:
correlations, such as might be enco
Page 155 and 156:
where n is the order of the expansi
Page 157 and 158:
terms by definition, and it can be
Page 159 and 160:
which is therefore independent of r
Page 161 and 162:
where the local energy, E L , is E
Page 163 and 164:
Another variant of variance minimiz
Page 165 and 166:
The energy minimization method used
Page 167 and 168:
valid. The first problem, which ari
Page 169 and 170:
• Is emin min energy too high? Th
Page 171 and 172:
It may be activated by setting vmc
Page 173 and 174:
that the number of configuration mo
Page 175 and 176:
• It is possible to use blip orbi
Page 177 and 178:
0.5 0.5 0.0 particle 1 det 1 : 9 or
Page 179 and 180:
The clearup twistav script can be u
Page 181 and 182:
In the infinite system limit, the s
Page 183 and 184:
Note that this has the k −2 diver
Page 185 and 186:
• The effective time step, Eq. (3
Page 187 and 188:
1 2 H He 1.00794 4.00260 3 4 5 6 7
Page 189 and 190:
and the Dirac delta function is δ(
Page 191 and 192:
33.2.2 Atomic densities K eywords:
Page 193 and 194:
The spin-density matrix is a two-by
Page 195 and 196:
33.3.3 Homogeneous and isotropic sy
Page 197 and 198:
33.4 Structure factor and spherical
Page 199 and 200:
33.5 One-body density matrix, two-b
Page 201 and 202:
[ where the approximation ρ (1)T
Page 203 and 204:
The figure shows the localization l
Page 205 and 206:
with F HFT mix = − F P mix = −
Page 207 and 208:
The input keyword to activate the c
Page 209 and 210:
To each walker r j , we assign a li
Page 211 and 212:
37 Magnetic fields and the fixed-ph
Page 213 and 214:
38 Analysis of the performance of C
Page 215 and 216:
the orbitals, α = 2 [11]. The use
Page 217 and 218:
39.2 Implementation basics and perf
Page 219 and 220:
• Use ‘endif’ and ‘enddo’
Page 221 and 222:
• Evidence of testing on serial a
Page 223 and 224:
B Appendix 2: Automatic testing of
Page 225 and 226:
• Delete any eepot.data and densi
Page 227 and 228:
* "Generic" CASINO_ARCHs are intend
Page 229 and 230:
- ‘head -n 1 /etc/redhat-release
Page 231 and 232:
for a single job in an ensemble of
Page 233 and 234:
inary executable. CASINO does not r
Page 235 and 236:
otherwise. The following tags are o
Page 237 and 238:
[2] V.R. Saunders, R. Dovesi, C. Ro
Page 239 and 240:
[50] W. Janke, Statistical Analysis
show all

CASINO manual - Theory of Condensed Matter

You also want an ePaper? Increase the reach of your titles

Delete template?

Save as template?