The xtb(1) program performs semiempirical quantummechanical
calculations. The underlying effective Hamiltonian is derived from density
functional tight binding (DFTB). This implementation of the xTB Hamiltonian
is currently compatible with the zeroth, first and second level
parametrisation for geometries, frequencies and non-covalent interactions
(GFN) as well as with the ionisation potential and electron affinity (IPEA)
parametrisation of the GFN1 Hamiltonian. The generalized born (GB) model
with solvent accessable surface area (SASA) is also available available in
this version. Ground state calculations for the simplified Tamm-Danceoff
approximation (sTDA) with the vTB model are currently not implemented.
The wide variety of input formats for the geometry are supported
by using the mctc-lib. Supported formats are:
•Xmol/xyz files (xyz, log)
•Turbomole’s coord, riper’s periodic
coord (tmol, coord)
•DFTB+ genFormat geometry inputs as cluster,
supercell or fractional (gen)
•VASP’s POSCAR/CONTCAR input files (vasp,
poscar, contcar)
•Protein Database files, only single files
(pdb)
•Connection table files, molfile (mol) and
structure data format (sdf)
•Gaussian’s external program input
(ein)
•JSON input with qcschema_molecule or
qcschema_input structure (json)
•FHI-AIMS' input files (geometry.in)
•Q-Chem molecule block inputs (qchem)
For a full list visit:
https://grimme-lab.github.io/mctc-lib/page/index.html
xtb(1) reads additionally .CHRG and .UHF files if present.
-c, --chrg INT
specify molecular charge as INT, overrides .CHRG
file and xcontrol option
-u, --uhf INT
specify number of unpaired electrons as INT,
overrides .UHF file and xcontrol option
--gfn INT
specify parametrisation of GFN-xTB (default = 2)
--gfnff, --gff
specify parametrisation of GFN-FF
--oniom METHOD LIST
use subtractive embedding via ONIOM method. METHOD
is given as inner:outer where inner can be orca, turbomole,
gfn2, gfn1, or gfnff and outer can be gfn2,
gfn1, or gfnff. The inner region is given as a comma separated
indices directly in the commandline or in a file with each index on a separate
line.
--etemp REAL
electronic temperature (default = 300K)
--esp
calculate electrostatic potential on VdW-grid
--stm
calculate STM image
-a, --acc REAL
accuracy for SCC calculation, lower is better (default =
1.0)
--vparam FILE
Parameter file for vTB calculation
--xparam FILE
Parameter file for xTB calculation (not used)
--alpb SOLVENT [STATE]
analytical linearized Poisson-Boltzmann (ALPB) model,
available solvents are acetone, acetonitrile, aniline,
benzaldehyde, benzene, ch2cl2, chcl3, cs2,
dioxane, dmf, dmso, ether, ethylacetate,
furane, hexandecane, hexane, methanol,
nitromethane, octanol, woctanol, phenol,
toluene, thf, water. The solvent input is not
case-sensitive. The Gsolv reference state can be chosen as reference or
bar1M (default).
-g, --gbsa SOLVENT [STATE]
generalized born (GB) model with solvent accessable
surface (SASA) model, available solvents are acetone,
acetonitrile, benzene (only GFN1-xTB), CH2Cl2,
CHCl3, CS2, DMF (only GFN2-xTB), DMSO,
ether, H2O, methanol, n-hexane (only GFN2-xTB),
THF and toluene. The solvent input is not case-sensitive. The
Gsolv reference state can be chosen as reference or bar1M
(default).
--cma
shifts molecule to center of mass and transforms
cartesian coordinates into the coordinate system of the principle axis (not
affected by ‘isotopes’-file).
--pop
requests printout of Mulliken population analysis
--molden
requests printout of molden file
--dipole
requests dipole printout
--wbo
requests Wiberg bond order printout
--lmo
requests localization of orbitals
--fod
requests FOD calculation
Note
You can only select one runtyp, only the first runtyp will
be used from the program, use implemented composite runtyps to perform
several operations at once.
--scc, --sp
performs a single point calculation
--vip
performs calculation of ionisation potential. This needs
the .param_ipea.xtb parameters and a GFN1 Hamiltonian.
--vea
performs calculation of electron affinity. This needs the
.param_ipea.xtb parameters and a GFN1 Hamiltonian.
--vipea
performs calculation of electron affinity and ionisation
potential. This needs the .param_ipea.xtb parameters and a GFN1
Hamiltonian.
--vfukui
performs calculation of Fukui indices.
--vomega
performs calculation of electrophilicity index. This
needs the .param_ipea.xtb parameters and a GFN1 Hamiltonian.
--grad
performs a gradient calculation
-o, --opt [LEVEL]
call
ancopt(3) to perform a geometry optimization, levels
from crude, sloppy, loose, normal (default), tight, verytight to extreme can
be chosen
--hess
perform a numerical hessian calculation on input
geometry
--ohess [LEVEL]
perform a numerical hessian calculation on an
ancopt(3)
optimized geometry
--bhess [LEVEL]
perform a biased numerical hessian calculation on an
ancopt(3) optimized geometry
--md
molecular dynamics simulation on start geometry
--metadyn [int]
meta dynamics simulation on start geometry, saving
int snapshots of the trajectory to bias the simulation
--omd
molecular dynamics simulation on
ancopt(3) optimized
geometry, a loose optimization level will be chosen
--metaopt [LEVEL]
call
ancopt(3) to perform a geometry optimization, then
try to find other minimas by meta dynamics
--path [FILE]
use meta dynamics to calculate a path from the input
geometry to the given product structure
--reactor
experimental
--modef INT
modefollowing algorithm. INT specifies the mode
that should be used for the modefollowing.
-I, --input FILE
--namespace STRING
give this
xtb(1) run a namespace. All files, even
temporary ones, will be named according to
STRING (might not work
everywhere).
--[no]copy
copies the xcontrol file at startup (default =
true)
--[no]restart
restarts calculation from xtbrestart (default =
true)
-P, --parallel INT
number of parallel processes
--define
performs automatic check of input and terminate
--json
write xtbout.json file
--citation
print citation and terminate
--license
print license and terminate
-v, --verbose
be more verbose (not supported in every unit)
-s, --silent
clutter the screen less (not supported in every
unit)
--ceasefiles
reduce the amount of output and files written
--strict
turns all warnings into hard errors
-h, --help
show help page
xtb(1) accesses a number of local files in the current working
directory and also writes some output in specific files. Note that not all
input and output files allow the --namespace option.
.CHRG
molecular charge as int
.UHF
Number of unpaired electrons as int
mdrestart
contains restart information for MD, --namespace
compatible.
pcharge
point charge input, format is real real
real real [int]. The first real is used as partial
charge, the next three entries are the cartesian coordinates and the last is
an optional atom type. Note that the point charge input is not affected by a
CMA transformation. Also parallel Hessian calculations will fail due to I/O
errors when using point charge embedding.
xcontrol
default input file in
--copy mode, see
xcontrol(7)
for details, set by
--input.
xtbrestart
contains restart information for SCC, --namespace
compatible.
charges
contains Mulliken partial charges calculated in SCC
wbo
contains Wiberg bond order calculated in SCC,
--namespace compatible.
energy
total energy in Turbomole format
gradient
geometry, energy and gradient in Turbomole format
hessian
contains the (not mass weighted) cartesian Hessian,
--namespace compatible.
xtbopt.xyz, xtbopt.coord
optimized geometry in the same format as the input
geometry.
xtbhess.coord
distorted geometry if imaginary frequency was found
xtbopt.log
contains all structures obtained in the geometry
optimization with the respective energy in the comment line in a XMOL
formatted trajectory
xtbsiman.log,xtb.trj.int
trajectories from MD
scoord.int
coordinate dump of MD
fod.cub
FOD on a cube-type grid
spindensity.cub
spindensity on a cube-type grid
density.cub
density on a cube-type grid
molden.input
MOs and occupation for visualisation and sTDA-xTB
calculations
pcgrad
gradient of the point charges
xtb_esp.cosmo
ESP fake cosmo output
xtb_esp_profile.dat
ESP histogramm data
vibspectrum
Turbomole style vibrational spectrum data group
g98.out, g98l.out, g98_canmode.out,
g98_locmode.out
g98 fake output with normal or local modes
.tmpxtbmodef
input for mode following
coordprot.0
protonated species
xtblmoinfo
centers of the localized molecular orbitals
lmocent.coord
centers of the localized molecular orbitals
tmpxx
number of recommended modes for mode following
xtb_normalmodes, xtb_localmodes
binary dump for mode following
xtbmdok
generated by successful MD
.xtbok
generated after each successful
xtb(1) run
.sccnotconverged
generated after failed SCC with printlevel=2
xtb(1) can generate the two types of warnings, the first warning
section is printed immediately after the normal banner at startup, summing
up the evaluation of all input sources (commandline, xcontrol, xtbrc). To
check this warnings exclusively before running an expensive calculation a
input check is implemented via the --define flag. Please, study this
warnings carefully!
After xtb(1) has evaluated the all input sources it immediately
enters the production mode. Severe errors will lead to an abnormal
termination which is signalled by the printout to STDERR and a non-zero
return value (usually 128). All non-fatal errors are summerized in the end
of the calculation in one block, right bevor the timing analysis.
To aid the user to fix the problems generating these warnings a
brief summary of each warning with its respective string representation in
the output will be shown here:
ANCopt failed to converge the optimization
geometry optimization has failed to converge in the given
number optimization cycles. This is not neccessary a problem if only a small
number of cycles was given for the optimization on purpose. All further
calculations are done on the last geometry of the optimization.
Hessian on incompletely optimized geometry!
This warning will be issued twice, once before the
Hessian, calculations starts (it would otherwise take some time before this
this warning could be detected) and in the warning block in the end. The
warning will be generated if the gradient norm on the given geometry is higher
than a certain threshold.