将vasp中分数坐标的POSCAR转化为笛卡尔坐标（无原子固定情况）

# -*- coding: utf-8 -*-
"""
Created on Wed Jan  1 19:22:26 2025
@author: Zhu
"""
with open('POSCAR')as xdat:
    lines = xdat.readlines()
a1,a2,a3 = lines[2].split(),lines[3].split(),lines[4].split()
a1 = [float(x) for x in a1]
a2 = [float(x) for x in a2]
a3 = [float(x) for x in a3]
atoms_num = lines[6].split()
atoms_num = [int(x) for x in atoms_num]
total_atoms = sum(atoms_num)
coord = []
for i in range(8,total_atoms+8):
    coord.append(lines[i].split())
coord = [[float(t) for s in sublist for t in s.split(', ')] for sublist in coord]
cartesian = []
for i in coord:
    px = i[0]*a1[0]+i[1]*a2[0]+i[2]*a3[0]
    py = i[0]*a1[1]+i[1]*a2[1]+i[2]*a3[1]
    pz = i[0]*a1[2]+i[1]*a2[2]+i[2]*a3[2]
    cartesian.append([px,py,pz])
with open('POSCAR+','w') as newpos:
    for i in range(0,7):
        newpos.write(lines[i])
    newpos.write("Cartesian\n")
    for i in cartesian:
        for j in i:
            newpos.write(str(j)+" ")
        newpos.write("\n")

参考：

图片来源：https://yxli8023.github.io/2020/09/25/Vasp-DC.html