JVASP-21825_BaBe2Si2O7
JARVIS-ID:JVASP-21825 Functional:optB88-vdW Primitive cell Primitive cell Conventional cell Conventional cell
Chemical formula:BaBe2Si2O7 Formation energy/atom (eV):-3.113 a 4.705 Å α:90.0 ° a 4.705 Å α:90.0 °
Space-group :Pmn2_1, 31 Relaxed energy/atom (eV):-6.0601 b 4.954 Å β:90.0 ° b 4.954 Å β:90.0 °
Calculation type:Bulk SCF bandgap (eV):6.056 c 11.729 Å γ:90.0 ° c 11.729 Å γ:90.0 °
Crystal system:orthorhombic Point group:mm2 Density (gcm-3):3.93 Volume (3):273.39 nAtoms_prim:24 nAtoms_conv:24
Download input files

Convergence [Reference]

Calculations are done using VASP software [Source-code]. Convergence on KPOINTS [Source-code] and ENCUT [Source-code] is done with respect to total energy of the system within 0.001 eV tolerance. Please note convergence on KPOINTS and ENCUT is generally done for target properties, but here we assume energy-convergence with 0.001 eV should be sufficient for other properties also. The points on the curves are obtained with single-point calculation (number of ionic steps, NSW=1 ). However, for very accurate calculations, NSW>1 might be needed.


Structural analysis [Reference]

The following shows the X-ray diffraction (XRD)[Source-code] pattern and the Radial distribution function (RDF) plots [Source-code]. XRD peaks should be comparable to experiments for bulk structures. Relative intensities may differ. For mono- and multi-layer structures , we take the z-dimension during DFT calculation for XRD calculations, which may differ from the experimental set-up.


Electronic structure [Reference]

The following shows the electronic density of states and bandstructure [Source-code]. DFT is generally predicted to underestimate bandgap of materials. Accurate band-gaps are obtained with higher level methods (with high computational requirement) such as HSE, GW , which are under progress. If available, MBJ data should be comparable to experiments also. Total DOS, Orbital DOS and Element dos [Source-code] buttons are provided for density of states options. Energy is rescaled to make Fermi-energy zero. In the bandstructure plot [Source-code], spin up is shown with blue lines while spin down are shown with red lines. Non-degenerate spin-up and spin-down states (if applicable) would imply a net orbital magnetic moment in the system. Fermi-occupation tolerance for bandgap calculation is chosen as 0.001.

High-symmetry kpoints based bandgap (eV): 6.037I


Electrostatic potential [Reference]

The following plot shows the plane averaged electrostatic potential (ionic+Hartree) along x, y and z-directions. The red line shows the Fermi-energy while the green line shows the maximum value of the electrostatic potential. For slab structures (with vacuum along z-direction), the difference in these two values can be used to calculate work-function of the material.


Optoelectronic properties Semi-local [Reference]

Incident photon energy dependence of optical is shown below [Source-code]. Only interband optical transitions are taken into account.Please note the underestimatation of band-gap problem with DFT will reflect in the spectra as well. For very accurate optical properties GW/BSE calculation would be needed, which is yet to be done because of their very high computational cost. Optical properties for mono-/multi-layer materials were rescaled with the actual thickness to simulation z-box ratio. Absorption coeffiecient is in cm-1 unit. Also, ionic contributions were neglected.

Dense k-mesh based bandgap is : 6.0564 eV

Static real-parts of dielectric function in x,y,z: 3.08,3.1,3.04


DFPT: IR-intensity, Piezoelecric and Dielectric tensors [Reference]

Calculations are done using density functional perturbation theory (DFPT) method for non-metallic systems for conventional cell and at Gamma-point in phonon BZ.

Static dielecric-tensor

8.59 0.0 0.0
0.0 9.04 0.0
0.0 0.0 9.46

Piezoelectric-stress-tensor (C/m2)

0.71 0.22 0.28 0.0 0.0 0.0
0.0 0.0 0.0 -0.01 0.0 0.0
0.0 0.0 0.0 0.0 0.0 0.06

Finite-difference: elastic tensor and derived phonon properties [Reference]

Elastic tensor calculated for the conventional cell of the system with finite-difference method [Source-code]. For bulk structures, elastic constants are given in GPa unit . For layered materials, the elastic constants are rescaled with respect to vacuum padding (see the input files) and the units for elastic coefficients are in N/m . Phonons obtained [Source-code] from this calculation are also shown.

WARNING: Please note we provide finite-size cell phonons only. At least 1.2 nm x1.2 nm x1.2 nm size cell or more is generally needed for obtaining reliable phonon spectrum, but we take conventional cell of the structure only. For systems having primitive-cell phonon representation tables, I denotes infrared activity and R denotes Raman active modes (where applicabale). Selection of particular q-point mesh can give rise to unphysical negative modes in phonon density of states and phonon bandstructre. The minimum thermal conductivity was calculated using elastic tensor information following Clarke and Cahill formalism.

Voigt-bulk modulus (KV): 91.28 GPa, Voigt-shear modulus (GV): 67.13 GPa

Reuss-bulk modulus (KR): 90.65 GPa, Reuss-shear modulus (GR): 66.61 GPa

Poisson's ratio: 0.2, Elastic anisotropy parameter: 0.05

Clarke's lower limit of thermal conductivity (W/(m.K)): 1.52

Cahill's lower limit of thermal conductivity (W/(m.K)): 1.65

Elastic tensor
191.3 43.5 35.3 -0.0 0.0 -0.0
43.5 195.7 55.2 0.0 0.0 -0.0
35.3 55.2 166.5 -0.0 0.0 -0.0
-0.0 0.0 -0.0 62.7 0.0 -0.0
0.0 -0.0 0.0 0.0 64.2 -0.0
0.0 -0.0 -0.0 -0.0 -0.0 68.9

Phonon mode (cm-1)
-0.04
-0.03
-0.01
75.37
81.85
97.84
98.66
107.32
112.08
117.57
122.34
175.27
187.9
200.88
204.35
206.71
211.14
220.81
235.61
266.33
295.75
299.08
323.0
334.32
342.32
364.15
373.54
380.48
381.97
416.19
420.99
426.58
434.81
446.31
450.97
458.74
482.73
503.09
504.99
532.98
563.14
563.4
594.94
603.45
628.18
629.58
671.86
676.72
711.23
715.41
722.34
730.44
737.43
753.73
757.5
788.54
788.69
803.13
875.49
891.11
905.39
906.29
923.54
931.77
933.44
946.12
950.18
957.92
967.97
970.75
981.59
1033.25

Point group

point_group_type: mm2

Visualize Phonons here
Phonon mode (cm-1) Representation
-0.04
-0.0442614253
-0.03
-0.0340271806
-0.01
-0.0104532889
75.37
75.3672165956
81.85
81.8493151285
97.84
97.8432956854
98.66
98.6561132715
107.32
107.315304656
112.08
112.078056495
117.57
117.568041145
122.34
122.338214406
175.27
175.265447732
187.9
187.895867286
200.88
200.876910081
204.35
204.350183677
206.71
206.712865718
211.14
211.140441683
220.81
220.813136822
235.61
235.613628942
266.33
266.328553322
295.75
295.746212336
299.08
299.08264642
323.0
323.003764253
334.32
334.324305369
342.32
342.324011356
364.15
364.148230182
373.54
373.536705391
380.48
380.476080367
381.97
381.968970935
416.19
416.19471811
420.99
420.990434583
426.58
426.576025791
434.81
434.806994273
446.31
446.312108697
450.97
450.967983703
458.74
458.74186189
482.73
482.732454544
503.09
503.085120259
504.99
504.989047204
532.98
532.980550769
563.14
563.142793798
563.4
563.39876353
594.94
594.940940952
603.45
603.451992419
628.18
628.179023452
629.58
629.576043682
671.86
671.857791387
676.72
676.722267191
711.23
711.227618646
715.41
715.405756778
722.34
722.344499879
730.44
730.442655491
737.43
737.428947993
753.73
753.727266727
757.5
757.495256336
788.54
788.539598002
788.69
788.694815802
803.13
803.133289636
875.49
875.488736381
891.11
891.105557096
905.39
905.390385382
906.29
906.287491942
923.54
923.541719588
931.77
931.765509857
933.44
933.443921767
946.12
946.123036655
950.18
950.176334381
957.92
957.924543278
967.97
967.971264431
970.75
970.751692592
981.59
981.59012707
1033.25
1033.252902

Thermoelectric properties [Reference]

Thermoelectric properties are calculated using BoltzTrap code [Source-code]. Electron and hole mass tensors (useful for semiconductors and insulators mainly)are given at 300 K [Source-code]. Following plots show the Seebeck coefficient and ZT factor (eigenvalues of the tensor shown) at 300 K along three different crystallographic directions. Seebeck coefficient and ZT plots can be compared for three different temperatures available through the buttons given below. Generally very high Kpoints are needed for obtaining thermoelectric properties. We assume the Kpoints obtained from above convergence were sufficient [Source-code].

WARNING: Constant relaxation time approximation (10-14 s) and only electronic contribution to thermal conductivity were utilized for calculating ZT.

Electron mass tensor (me unit)

0.38 -0.0 0.0
-0.0 0.37 0.0
0.0 0.0 0.33

Hole mass tensor (me unit)

4.67 -0.0 0.0
-0.0 19.14 -0.0
0.0 -0.0 7.48

n-& p-type Seebeck coeff. (µV/K), power-factor (µW/(mK2)), conductivity (1/(*m)), zT (assuming lattice part of thermal conductivity as 1 W/(mK)) at 600K and 1020 cm-3 doping. For mono/multi-layer materials consider Seebeck-coeff only.)

Property xx yy zz
n-Seebeck -93.81 -93.77 -91.0
n-PowerFactor 413.1 441.86 795.43
n-Conductivity 49888.56 50211.94 90462.59
n-ZT 0.15 0.16 0.23
p-Seebeck 416.82 447.71 458.52
p-PowerFactor 216.85 372.5 1143.97
p-Conductivity 1081.86 2144.0 5441.26
p-ZT 0.13 0.22 0.66

See also

Links to other databases or papers are provided below


mp-12797

MP link
mp-12797

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