VASP_Optics_BSE

VASP_Optics_BSE

VASP官网例子(以Si为例)

第一步:opt
第二步:DFT groundstate calculation
#Si_dft_exc
System = Si
PREC = Normal    精度参数,决定ECNUT,默认就是Normal
ENCUT = 250.0    截断能
ISMEAR = 0        
SIGMA = 0.01
KPAR = 2         KPAR是要并行处理的k点数,(总核数/KPAR)个核同时处理一个k点。所以需要整除
EDIFF = 1.E-6
第三步:Obtain DFT virtual orbitals(empty states)
#Si_dft_exc
System = Si
PREC = Normal            精度参数,决定ECNUT,默认就是Normal
ENCUT = 250.0            截断能
ALGO = EXACT             产生空带
NELM = 1
ISMEAR = 0
SIGMA = 0.01
KPAR = 2                KPAR是要并行处理的k点数,(总核数/KPAR)个核同时处理一个k点。所以需要整除
NBANDS = 128            较上一步要增大NBANDS数量,产生空带。
LOPTICS = .TRUE.        打开之后生成WAVEDER 文件,第四步需要用到 WAVECAR 和 WAVEDER
LPEAD = .TRUE.          必须要设置这个参数,打开之后使用有限差分方法计算,通常跟LOPTICS=.TRUE. 和LEPSILON=.TRUE. 一起使用
OMEGAMAX = 40           最大频率(eV)
第四步:RPA quasiparticles with single-shot GW(G0W0)
#Si_gw
System = Si
PREC = Normal                精度参数,决定ECNUT,默认就是Normal
ENCUT = 250.0                截断能
ALGO = GW0  
ISMEAR = 0
SIGMA = 0.01 
ENCUTGW = 150            响应函数的截断能
NELM = 1
NOMEGA = 50
OMEGATL = 280               频率网格的最大频率
KPAR = 2                    KPAR是要并行处理的k点数,(总核数/KPAR)个核同时处理一个k点。所以需要整除
#NBANDSO=4 ; NBANDSV=8 ; LADDER=.TRUE. ; LUSEW=.TRUE.
NBANDS = 128
NBANDSGW = 12                 GW计算中更新的轨道数
LWAVE = .TRUE.                默认值就是写入WAVECAR,必须要生成WAVECAR,以便更新单电子GW能量
PRECFOCK = Normal            默认值就是Normal,控制ecact交换的FFT网格
#LOPTICS = .TRUE.  这一行是我自己加的
第五步:Plot IPA dielectric function using GW0 quasiparticle energies(可选)
#Si_gw
System = Si
PREC = Normal                精度参数,决定ECNUT,默认就是Normal
ENCUT = 250.0                截断能
ALGO = Nothing
NELM = 1
ISMEAR = 0
SIGMA = 0.01        
KPAR = 2                    KPAR是要并行处理的k点数,(总核数/KPAR)个核同时处理一个k点。所以需要整除
NBANDS = 128    
LWAVE = .FALSE.
LOPTICS = .TRUE.
LPEAD = .TRUE.
OMEGAMAX = 40                最大频率(eV)
第六步:The BSE calculation (第四步-->第六步)

这一步不能设置KPAR = 2

#Si_bse
System = Si
PREC = Normal                精度参数,决定ECNUT,默认就是Normal
ENCUT = 250.0                截断能
ALGO = BSE 
ANTIRES = 0                  默认值是0,但是手册中的意思是设置为1是最好的???
ISMEAR = 0
SIGMA = 0.01
ENCUTGW = 150                响应函数的截断能
EDIFF = 1.E-8 # default 1.E-4
NBANDS = 128
NBANDSO = 4                  决定占据轨道数量
NBANDSV = 8                  决定未占据轨道数量
OMEGAMAX = 20                最大频率(eV)
PRECFOCK = Normal            默认值就是Normal,控制ecact交换的FFT网格

VASP always uses the orbitals closest to the Fermi-level, and NBANDSO(Nocc) and NBANDSV(Nvirtual) determines how many occupied and unoccupied orbitals are included. The defaults are fairly conservative and equal the total number of electrons/2 (this usually implies that all occupied state are included). For highly accurate results, NBANDSV often needs to be increased, whereas for large systems one is often forced to reduce both values to much smaller numbers. Sometimes qualitative results for band like Wannier-Mott excitons can be obtained even with a single conduction and valence band.

VASP总是使用最靠近费米级的轨道,NBANDSO(Nocc)和NBANDSV(Nvirtual)确定包含多少占用和未占用的轨道。 默认值相当“保守”并且等于电子总数/ 2(这通常意味着包括所有占用状态)。 为了获得高度精确的结果,需要增加NBANDSVoften,而对于大型系统,通常需要将两个值减少到更小的数量。 有时,即使使用单个导带和价带,也可以获得类似Wannier-Mott激子的定性结果。

一个成功的例子

scf
SYSTEM = MoSe2
PREC = Normal
ENCUT = 300
ISMEAR = 0
SIGMA = 0.05
EDIFF = 1E-4
KPAR = 2

exact
SYSTEM = MoSe2
PREC = Normal
ENCUT = 300
ISMEAR = 0
SIGMA = 0.05
EDIFF = 1E-4
KPAR = 2
ALGO = EXACT
NELM = 1
NBANDS = 36
LOPTICS = .TRUE.
LPEAD = .TRUE.
OMEGAMAX = 20

gw0
SYSTEM = MoSe2
PREC = Normal
ENCUT = 300
ISMEAR = 0
SIGMA = 0.05
EDIFF = 1E-4
KPAR = 2
ALGO = GW0
NELM = 1
NOMAGE = 48
OMEGATL = 200
ENCUTGW = 150
NBANDSGW = 12
NBANDS = 36
LOPTICS = .TRUE.
LPEAD = .TRUE.
OMEGAMAX = 20
PRECFOCK = Normal

gw0_ipa
SYSTEM = MoSe2
PREC = Normal
ENCUT = 300
ISMEAR = 0
SIGMA = 0.05
EDIFF = 1E-4
KPAR = 2
ALGO = Nothing
NELM = 1
NBANDS = 36
LOPTICS = .TRUE.
LPEAD = .TRUE.
OMEGAMAX = 20

bse
SYSTEM = MoSe2
PREC = Normal
ENCUT = 300
ISMEAR = 0
SIGMA = 0.05
EDIFF = 1E-4
#KPAR = 2                不能设置 KPAR = 2
ALGO = BSE
NOMAGE = 48
OGEMATL = 200
ENCUTGW = 150
#NBANDSGW = 12
NBANDSO = 6
NBANDSV = 6
NBANDS = 36
#LOPTICS = .TRUE.
#LPEAD = .TRUE.
OMEGAMAX = 20
PRECFOCK = Normal

一个成功的INCAR.BSE
注意:该任务极其耗内存
SYSTEM = MoSe2
PREC = Normal
ENCUT = 300
ISMEAR = 0
SIGMA = 0.05
EDIFF = 1E-4
ALGO = BSE
NOMAGE = 48
OGEMATL = 200
ENCUTGW = 150
NBANDSO = 4
NBANDSV = 8
NBANDS = 96
OMEGAMAX = 20
PRECFOCK = Normal
暂无评论

发送评论 编辑评论


				
上一篇
下一篇